WASHINGTON – The BP oil rig explosion and spill wasn’t about anyone purposely sacrificing safety for money, investigators on a special presidential commission said Monday. Instead it was more about seemingly acceptable risks adding up to disaster.

Investigators at the commission’s hearing outlined more than a dozen decisions that at the time seemed questionable but also explainable. It was how those cascaded and crashed together that fueled catastrophe.

Yet there was no evidence of a conscious decision on the BP rig to do things on the cheap at the expense of safety, investigators stressed several times. Likewise, representatives of the companies involved in the disaster denied that corners were cut because of cost.

Critics — including a top academic, a congressman and people on the polluted Bayou — are balking at what they see as something close to a free pass for BP’s history of cost cutting. In the first nonpolitical and independent investigation of the disaster, commission officials say they aren’t excusing BP at all, but pointing out there was no clear single decision that came down solely to money.

“Anytime you are talking about a million and a half dollars a day, money enters in. All I am saying is human beings did not sit there and sell safety down the river for dollars on the rig that night,” said commission chief attorney Fred H. Bartlit Jr.

That doesn’t mean that a general culture of cost cutting wasn’t an issue, added commission co-chairman Bob Graham, the former Florida senator and governor. Graham wrapped up the day by saying he was worried that there was “a compulsion to get this rig completed in that April 19-April 20 timetable.”

And panel co-chairman William K. Reilly said in an interview after the hearing that BP does deserve a good share of blame: “A lot of the key decisions were in fact made by BP.” He said that while it might look as if the commission wasn’t concerned about the culture of cost cutting at BP, it will address that broader corporate problem in the future.

Halliburton Co., which had the crucial job of cementing the well, was on the hot seat as much as BP on Monday, clashing more often with investigators than the oil company. And the commission still hasn’t dealt with the blowout preventer, a key instrument, because it is still being examined.

Bartlit, the panel’s chief investigator, revealed in a letter last month that testing on cement mixtures similar to those used in the well showed that the formula was unstable before the blowout, but BP and Halliburton used it anyway. Bartlit said the companies should have reconsidered the type of cement used in the well. Cement is an essential barrier to preventing blowouts.

Led by commission investigators, BP Vice President Mark Bly said Halliburton officials were slow about testing and results.

Not everyone agrees that small decisions along the way led to the disaster. One of the nation’s top technological disaster academics said the spill commission was a “cover-up” from the White House. Charles Perrow, a Yale University professor who wrote the disaster sociology classic “Normal Accidents” said the investigation was overlooking BP’s track record of disasters that have come after cost cutting.

“There’s a long history of dollars versus safety at this organization,” Perrow said in a telephone interview with The Associated Press. He referred specifically to BP’s 2005 Texas City oil refinery explosion in which federal officials cited a culture of cost cutting at the expense of safety. In 2006, BP’s lack of leak detection caused a massive pipeline spill, the largest on Alaska’s North Slope to date.

Reilly, chief of the federal Environmental Protection Agency under President George H.W. Bush, told the AP he went into the investigation expecting to conclude that safety was traded for dollars but didn’t find that to be so. Instead, what investigators found was “a series of first challenging situations” and some choices that could go either way compounded by “hard to explain decisions.”

“And they add up to a disaster,” Reilly said.

The commission came up with 13 preliminary temporary conclusions. Like BP, it found that the oil and gas traveled up the center of the pipe in the well, rather than up the sides — a finding that was disputed by Halliburton on Monday. If the blowout started in the space between the pipe and the underground rock, Halliburton’s cement would be less of a factor.

Another question is why the blowout preventer — the last defense against a runaway well — failed to block the flow of oil and gas. Bartlit said the team would await a forensic analysis before drawing conclusions. The blowout preventer is now protected evidence in a federal court case.

University of California at Berkeley engineering professor Bob Bea, an expert in both offshore oil rigs and technological disasters, said in general he agreed with the spill commission’s findings. He suggested the problem wasn’t a specific safety-for-money decision made on the rig, but a lack of understanding of the dangers and trade-offs involved.

Daniel Becnel, a Louisiana lawyer suing BP and others, called the commission’s finding “absolutely absurd.” He also took issue with Bartlit’s endorsement of BP’s view of events.

“They are pasting over because they know the government is going to be a defendant sooner or later in this litigation,” Becnel said.