NEW ORLEANS — Over six days in May, far from the familiar choreography of Washington hearings, federal investigators grilled workers involved in the Deepwater Horizon disaster in a chilly, sterile conference room at a hotel near the airport here.

The six-member panel of Coast Guard and Minerals Management Service officials pressed for answers about what occurred on the rig on April 20 before it exploded. They wanted to know who was in charge, and heard conflicting answers.

They pushed for more insight into an argument on the rig that day between a manager for BP, the well’s owner, and one for Transocean, the rig’s owner, and asked Curt R. Kuchta, the rig’s captain, how the crew knew who was in charge.

“It’s pretty well understood amongst the crew who’s in charge,” he said.

“How do they know that?” a Coast Guard investigator asked.

“I guess, I don’t know,” Captain Kuchta said. “But it’s pretty well — everyone knows.”

Looking annoyed, Capt. Hung Nguyen of the Coast Guard, one of the chief federal investigators, shook his head. The exchange confirmed an observation he had made earlier in the day at the hearing.

“A lot of activities seem not very tightly coordinated in the way that would make me comfortable,” he said. “Maybe that’s just the way of business out there.”

Investigators have focused on the minute-to-minute decisions and breakdowns to understand what led to the explosion of the Deepwater Horizon, killing 11 people and setting off the largest oil spill in United States history and an environmental disaster. But the lack of coordination was not limited to the day of the explosion.

New government and BP documents, interviews with experts and testimony by witnesses provide the clearest indication to date that a hodgepodge of oversight agencies granted exceptions to rules, allowed risks to accumulate and made a disaster more likely on the rig, particularly with a mix of different companies operating on the Deepwater whose interests were not always in sync.

And in the aftermath, arguments about who is in charge of the cleanup — often a signal that no one is in charge — have led to delays, distractions and disagreements over how to cap the well and defend the coastline. As a result, with oil continuing to gush a mile below the surface in the Gulf of Mexico, the laws of physics are largely in control, creating the daunting challenge of trying to plug a hole at depths where equipment is straining under more than a ton of pressure per square inch.

Tad W. Patzek, chairman of the Petroleum and Geosystems Engineering Department at the University of Texas, Austin, has analyzed reports of what led to the explosion. “It’s a very complex operation in which the human element has not been aligned with the complexity of the system,” he said in an interview last week.

His conclusion could also apply to what occurred long before the disaster.

Exceptions Are the Rule

Deepwater oil production in the gulf, which started in 1979 but expanded much faster in the mid-1990s with new technology and federal incentives, is governed as much by exceptions to rules as by the rules themselves.

Under a process called “alternative compliance,” much of the technology used on deepwater rigs has been approved piecemeal, with regulators cooperating with industry groups to make small adjustments to guidelines that were drawn up decades ago for shallow-water drilling.

Of roughly 3,500 drilling rigs and production platforms in the gulf, fewer than 50 are in waters deeper than 1,000 feet. But the risks and challenges associated with this deeper water are much greater.

“The pace of technology has definitely outrun the regulations,” Lt. Cmdr. Michael Odom of the Coast Guard, who inspects the rigs, said last month at a hearing.

As a result, deepwater rigs operate under an ad hoc system of exceptions. The deeper the water, the further the exceptions stretch, not just from federal guidelines but also often from company policy.

So, for example, when BP officials first set their sights on extracting the oily riches under what is known as Mississippi Canyon Block 252 in the Gulf of Mexico, they asked for and received permission from federal regulators to exempt the drilling project from federal law that requires a rigorous type of environmental review, internal documents and federal records indicate.

As BP engineers planned to set certain pipes and casings for lining the well in place in the ocean floor, they had to get permission from company managers to use riskier equipment because that equipment deviated from the company’s own design and safety policies, according to internal BP documents obtained by The New York Times.

And when company officials wanted to test the blowout preventer, a crucial fail-safe mechanism on the pipe near the ocean floor, at a lower pressure than was federally required, regulators granted an exception, documents released last week show.

Regulators granted yet another exception when BP sought to delay mandatory testing of that blowout preventer because they had lost “well control,” weeks before the rig exploded, BP e-mail messages show.

The Minerals Management Service, which regulates offshore drilling, went along with these requests partly because the agency has for years had a dual role of both fostering and policing the industry — collecting royalty payments from the drilling companies while also levying fines on them for violations of law.

Its safety inspections usually consist of helicopter visits to offshore rigs to sift through company reports of self-administered tests.

Even Ken Salazar, the interior secretary, who oversees the minerals agency, has said that oil companies have a history of “running the show” at the agency, a problem he has vowed to correct.

The minerals agency shares responsibility for oversight of drilling in the gulf with many others. The Environmental Protection Agency and others review offshore drilling for potential damage to wildlife and the environment. The Coast Guard inspects vessels for seaworthiness and licenses crew members to work on the rigs. The National Oceanic and Atmospheric Administration monitors dangerous weather conditions over deep seas.

And regulatory duties extend even past the federal government. Foreign countries, or “flag states,” where many oil rigs are registered, have their own sets of safety requirements and inspections.

Regulations have not kept up with the risks that deepwater drilling poses.

On the Deepwater Horizon, for example, the minerals agency approved a drilling plan for BP that cited the “worst case” for a blowout as one that might produce 250,000 barrels of oil per day, federal records show. But the agency did not require the rig to create a response plan for such a situation.

If a blowout were to occur, BP said in its plan, the first choice would be to use a containment dome to capture the leaking oil. But regulators did not require that a containment dome be kept on the rig to speed the response to a spill. After the rig explosion, BP took two weeks to build one on shore and three days to ship it out to sea before it was lowered over the gushing pipe on May 7. It did not work.

(The rig’s “spill response plan,” provided to The Times, includes a Web link for a contractor that goes to an Asian shopping Web site and also mentions the importance of protecting walruses, seals and sea lions, none of which inhabit the area of drilling. The agency approved the plan.)

More broadly, regulators have not required technology and strategies for dealing with deepwater spills to be improved.

Engineers trying to control the blowout are using the same tactics they used in 1979 when the Ixtoc I well blew up in the Bay of Campeche off the coast of Mexico. In the earlier blowout, they first tried lowering a containment dome over the leak. When that failed, they unsuccessfully tried to inject golf balls and other material in a move called a junk shot, which was also tried and abandoned for the Deepwater Horizon.

Questions of oversight also came up in the New Orleans hearings last month. For example, Michael J. Saucier, an official with the Minerals Management Service, said that his agency “highly encouraged” — but did not require — companies to have backup systems to trigger blowout preventers in case of an emergency.

“Highly encourage?” Captain Nguyen of the Coast Guard asked. “How does that translate to enforcement?”

“There is no enforcement,” Mr. Saucier answered.

Problems Early On

In some ways it was jinxed from the start.

As early as June 2009, BP engineers had expressed concerns in internal documents about using certain casings for the well because they violated the company’s safety and design guidelines. But they proceeded with those casings.

Mechanical problems started in March with the Deepwater, setting the stage for the April 20 explosion.

More than five weeks before disaster, the rig was hit by several sudden pulsations of gas called “kicks” and a pipe had become stuck in the well. The blowout preventer, designed to seal the well in an emergency, had been discovered to be leaking fluids at least three times.

Dealing with these problems required teamwork, a challenge to the throng of different companies with responsibilities on the rig. Of the 126 people present on the day of the explosion, only eight were employees of BP. The interests of the workers did not always align.

In testimony to government investigators, rig workers repeatedly described a “natural conflict” between BP, which can make more money by completing drilling jobs quickly, and Transocean, which receives a leasing fee from BP every day that it continues drilling.

Halliburton was also on hand to provide cementing services, while a subsidiary monitored various drilling fluids. A different company provided drilling fluid systems, another provided technicians to operate the remote-control vehicles that are they eyes of the rig crew deep underwater, and yet another provided the well casing.

Amid this tangle of overlapping authority and competing interests, no one was solely responsible for ensuring the rig’s safety, and communication was a constant challenge.

“I don’t have a feeling that there is somebody who has a handle on the coordination of all the activities on this vessel, going from routine to crisis,” Captain Nguyen said during one hearing. “BP is in charge of certain things, Transocean is in charge of certain things.”

Financial concerns added pressures on the rig.

BP had fallen behind schedule and over budget, paying roughly $500,000 a day to lease the rig from Transocean. The rig was 43 days late for starting a new drilling job for BP by the day of the explosion, a delay that had already cost the company more than $21 million.

With the clock ticking, bad decisions went unchecked, warning signs went unheeded and small lapses compounded.

On April 1, a job log written by a Halliburton employee, Marvin Volek, warns that BP’s use of cement “was against our best practices.”

An April 18 internal Halliburton memorandum indicates that Halliburton again warned BP about its practices, this time saying that a “severe” gas flow problem would occur if the casings were not centered more carefully.

Around that same time, a BP document shows, company officials chose a type of casing with a greater risk of collapsing.

Despite noticing cementing problems, BP skipped a quality test of the cement around the pipe. Federal regulators also gave the rig a pass at several critical moments. After the rig encountered several problems, including the gas kicks and the pipe stuck in the well, the regulators did not demand a halt to the operation. Instead, they gave permission for a delay in a safety test of the blowout preventer.

An initial investigation by BP points to a range of missteps.

Tests shortly before the well blew out found a buildup of pressure that was an “indicator of a very large abnormality,” BP concluded and disclosed to Congress in a preliminary report last month. Yet, the rig team was satisfied after another test was deemed successful, and it proceeded.

About 10 hours before the explosion, the challenges of trying to keep the pressure in the well under control led to an argument among the workers about how best to finish the well and move the rig to the next site.

Douglas Brown, a Transocean mechanic on the rig, told investigators that an unnamed BP official whom he called “the company man” had instructed rig workers to execute a new plan for removing the riser and sealing the well. Mr. Brown testified that workers thought the plan was too risky. But he could not hear details of the argument that ensued.

“The company man was basically saying, ‘Well, this is how it’s going to be,’ ” Mr. Brown told investigators at a hearing on May 26 near New Orleans, adding that the Transocean rig workers “reluctantly agreed.”

When the explosion occurred around 9:50 p.m. on April 20, there was pandemonium on the rig. Most workers headed for lifeboats. Others rescued shipmates trapped under equipment. On the bridge, Captain Kuchta gathered with at least eight other managers and crew members to decide on an emergency plan.

Steve Bertone, the chief engineer for Transocean, wrote in his witness statement that he ran up to the bridge where he heard Captain Kuchta screaming at a worker, Andrea Fleytas, because she had pressed the distress button without authorization.

Mr. Bertone turned to another worker and asked him if he had called to shore for help but was told he did not have permission to do so. Another manager tried to give the go-ahead, the testimony said, but someone else said the order needed to come from the rig’s offshore installation manager.

A Strained Partnership

After the spill, the government and BP were supposed to cooperate, partly a consequence of laws written after the 1989 Exxon Valdez spill that were intended to make polluters more accountable for cleaning up their own messes.

One example of what was supposed to be a unified front was the Joint Information Center. Housed in a Shell-owned training and conference center in Robert, La., the center includes roughly 65 employees, 10 of whom work for BP. Together, they write and issue news releases and coordinate posts on a Web site, Facebook and Twitter.

But the partnership between BP and the government has strained along with the failure of efforts to plug the well. Mr. Salazar, for example, assured the public on May 2 that the administration was keeping its “boot on the neck” of BP. Next he was being publicly chastised by President Obama for using antagonistic language.

BP’s chief executive, Tony Hayward, told reporters at one point that the spill was “relatively tiny.” Federal officials soon released estimates indicating that the spill had far outpaced the Exxon Valdez disaster.

Under intense media scrutiny, at least a dozen federal agencies have taken part in the spill response, making decision-making slow, conflicted and confused, as they sought to apply numerous federal statutes.

In one stark example of government disputes, internal e-mail messages from the minerals agency obtained by The Times reveal a heated debate over whether to ignore some federal environmental laws about gas emissions in an effort to speed the drilling of relief wells.

One agency official, Michael Tolbert, warned colleagues on April 24 that emissions of nitrous oxide from the well were “pretty far over the exemption level,” an issue that his colleague Tommy Broussard said could result in “BP wasting time” on environmental safeguards in a way that would be “completely stupid.”

But a third colleague, Elizabeth Peuler, intervened to demand that the agency take “no shortcuts.”

“Not even for this one,” she said. “Perhaps even especially for this one.”

Debates over the speed — or lack thereof — of the government response have also played out in Louisiana, where state officials spent much of May repeatedly seeking permission from the federal government to construct up to 90 miles of sand barriers to prevent oil from reaching the wetlands.

For three weeks, as the giant slick crept closer to shore, officials from the White House, Coast Guard, Army Corps of Engineers, Fish and Wildlife Service, National Oceanic and Atmospheric Administration and Environmental Protection Agency debated the best approach.

They ultimately approved the use of only one barrier, called a berm, to be paid for by BP.

Comparing the federal government’s response to “telling a drowning man to wait,” Gov. Bobby Jindal of Louisiana asked: If one berm is safe, then why not the 23 others that he had requested? Slowly, the federal government approved more berms.

From the start, BP had played down the extent of the problem in miscalculating the rate of the leak and in denying the existence of underwater oil plumes. By deferring to the company, federal officials underestimated the problem they were facing and thus what was needed to respond to it.

It took more than a week after the explosion for the homeland security secretary, Janet Napolitano, to declare, on April 29, “a spill of national significance” a legal categorization that was needed before certain federal assistance could be authorized.

Because of such delays, critics have charged, more coastline will be hit, more animals will die, more habitats will be ruined and more money will be lost in tourism, fishing and real estate.

And yet, the administration is limited in its ability to divorce itself from BP, because federal officials rely on the company for technology, personnel and financing for the cleanup. The relationship reached a turning point last week when the administration said the national incident commander, Adm. Thad W. Allen of the Coast Guard, would start giving solo briefings. He will no longer share a podium with BP, which will offer its own briefings.

That move, however, does not resolve the matter of who is actually in charge in the gulf — of ensuring safety and regulating the dangerous extraction of vast riches under the deepest waters there, as well as of handling the continuing emergency.

The question is proving equally vexing as investigators try to place blame for events on the rig the day of the explosion— as was clear on Tuesday when Attorney General Eric H. Holder Jr. announced that he had begun a criminal investigation.

Citing “a wide range of possible violations,” Mr. Holder declined to specify the target of the investigation, because, he said, the authorities were still not clear on “who should ultimately be held liable.”