NEW ORLEANS — In an internal report released Wednesday, BP blames itself, other companies’ workers and a complex series of failures for the massive Gulf of Mexico oil spill and the drilling rig explosion that preceded it.

The 193-page report was posted on the company’s website even though investigators have not yet begun to fully analyze a key piece of equipment, the blowout preventer, that should have cut off the flow of oil from the ruptured well but did not.

That means BP’s report is far from the definitive ruling on the blowout’s causes, but it may provide some hint of the company’s legal strategy — spreading the blame among itself, rig owner Transocean, and cement contractor Halliburton — as it faces hundreds of lawsuits and possible criminal charges over the spill. Government investigators and congressional panels are looking into the cause as well.

“This report is not BP’s mea culpa,” said Rep. Edward J. Markey, D-Mass., a frequent BP critic and a member of a congressional panel investigating the spill. “Of their own eight key findings, they only explicitly take responsibility for half of one. BP is happy to slice up blame, as long as they get the smallest piece.”

Robert Gordon, an attorney whose firm represents more than 1,000 fisherman, hotels, and restaurants affected by the spill, was more blunt.

“BP blaming others for the Gulf oil disaster is like Bernie Madoff blaming his accountant,” he said.

Members of Congress, industry experts and workers who survived the rig explosion have accused BP’s engineers of cutting corners to save time and money on a project that was 43 days and more than $20 million behind schedule at the time of the blast.

BP’s report acknowledged, as investigators have previously suggested, that its engineers and employees of Transocean misinterpreted a pressure test of the well’s integrity. It also blamed employees on the rig from both companies for failing to respond to warning signs that the well was in danger of blowing out.

Mark Bly, BP’s chief investigator, said at a briefing in Washington that the internal report was a reconstruction of what happened on the rig based on the company’s data and interviews with mostly BP employees and was not meant to focus on assigning blame. The six-person investigating panel only had access to a few workers from other companies, and samples of the actual cement used in the well were not released.

Outgoing BP chief Tony Hayward, who is being replaced Oct. 1 by American Bob Dudley, said in a statement that a bad cement job and a failure of a barrier at the bottom of the well let oil and gas leak out.

Transocean blasted BP’s report, calling it a self-serving attempt to conceal the real cause of the explosion, which it blamed on what it called “BP’s fatally flawed well design.”

“In both its design and construction, BP made a series of cost-saving decisions that increased risk — in some cases, severely,” Transocean said.

Halliburton said in a statement of its own that it found a number of omissions and inaccuracies in the report and is confident the work it completed on the well met BP’s specifications.

“Contractors do not specify well design or make decisions regarding testing procedures as that responsibility lies with the well owner,” the statement said.

An AP analysis of the report shows that the words “blame” and “mistake” never appear. “Fault” shows up 20 times, but only once in the same sentence as the company’s name.

Steve Yerrid, special counsel on the oil spill for Florida Gov. Charlie Crist, said the report clearly shows the company is attempting to spread blame for the well disaster, foreshadowing what will be a likely legal effort to force Halliburton and Transocean, and perhaps others, to share costs such as paying claims and government penalties.

In midday trading in New York, BP shares were up $1.15, or 3 percent, to $38.32.

Several divisions of the U.S. government, including the Justice Department, Coast Guard and Bureau of Ocean Energy Management, Regulation and Enforcement, are also investigating the explosion.

The blowout preventer was raised from the water off the coast of Louisiana on Saturday. As of Tuesday afternoon, it had not reached a NASA facility in New Orleans where government investigators planned to analyze it, so those conclusions were not part of BP’s report.

Retired Coast Guard Adm. Thad Allen, the government’s point man on the spill response, said the BP report will add to investigators’ understanding “but is not the end-all-be-all ... about why it happened and what needs to happen in the future.”

The rig explosion killed 11 workers and sent 206 million gallons of oil spewing from BP’s undersea well.

Investigators know the explosion was triggered by a bubble of methane gas that escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before igniting.

But they don’t know exactly how or why the gas escaped. And they don’t know why the blowout preventer didn’t seal the well pipe at the sea bottom after the eruption, as it was supposed to.

There were signs of problems prior to the explosion, including an unexpected loss of fluid from a pipe known as a riser five hours before the explosion that could have indicated a leak in the blowout preventer.

Witness statements show that rig workers talked just minutes before the blowout about pressure problems in the well.

At first, nobody seemed too worried, workers have said. Then panic set in.

Workers called their bosses to report that the well was “coming in” and that they were “getting mud back.” The drilling supervisor, Jason Anderson, tried to shut down the well.

It didn’t work. At least two explosions turned the rig into an inferno.

In its report, BP defended the well’s design, which has been criticized by industry experts. It also said “more thorough review and testing by Halliburton” and “stronger quality assurance” by BP’s well team well might have identified potential flaws and weaknesses in the design for the cement job.

Other conclusions in the report include:

— BP says its use of six centralizers, key devices used as part of the process to plug a well, instead of the 21 recommended by Halliburton likely did not contribute to the cement’s failure. Congress has questioned BP’s decision, because centralizers ensure casing runs down the center of the well bore and an imperfect seal could allow oil and gas to shoot up.

— BP said that while drilling the well on March 8, more than a month before the disaster, there was a “kick,” or fluid entering the well bore from the oil reservoir, that wasn’t noticed for 33 minutes. BP says there’s no evidence Transocean took any documented, corrective actions with the rig crew either to acknowledge or address the response time.

— Workers realized eight minutes before the blast that flammable oil and gas was traveling up the pipe connecting the rig to the well head, although data revealed that would happen 40 minutes before the explosion.

— The blowout preventer failed to do its job in part because equipment was faulty but also because it was damaged during the explosion.

— The drilling crew routed the flow from the blownout well to a system on the rig instead of overboard, a decision that allowed gas to get into ventilation systems, where it caught fire.