Massey Energy Co. recklessly ignored safety and allowed dangerous conditions to build inside a West Virginia mine until a blast last year killed 29 men in the deadliest U.S. coal accident since 1970, according to an independent report released Thursday.

The report by a former top federal mine regulator, commissioned by the state's then-governor, said Massey could have prevented the April 2010 disaster with standard safety practices, including better ventilation to reduce potentially explosive levels of gas and dust in the tunnels.

"A company that was a towering presence in the Appalachian coalfields operated its mines in a profoundly reckless manner, and 29 coal miners paid with their lives for the corporate risk-taking," the study concluded.

The study supported the federal government's theory that methane gas mixed with huge volumes of explosive coal dust turned a small fireball into a preventable earth-shattering explosion

"The disaster at Upper Big Branch was manmade and could have been prevented had Massey Energy followed basic, well-tested and historically proven safety procedures," investigators wrote.

Virginia-based Massey did not immediately respond. It is in the process of being acquired by Alpha Natural Resources. Massey executives have declined to be interviewed by investigators.

The report, released online at the same time it was presented privately to families of the victims, is the first of several that are expected. State and federal investigators are pursuing their own investigations, while federal prosecutors conduct a criminal investigation.

The 113-page report was compiled by a team led by former federal Mine Safety and Health Administration chief J. Davitt McAteer, who was appointed by then-Gov. Joe Manchin to examine the April 5, 2010, explosion.

McAteer's report has 11 findings and 52 recommendations, ranging from better monitoring of underground conditions to subjecting companies' boards of directors to penalties if they fail to make safety a priority.

Federal officials praised the findings as vindication of their theory.

"The finding is that this was a preventable disaster and that's something I believed from day one," Mine Safety and Health Administration director Joe Main told The Associated Press. "The mine operator just miserably failed to comply with the law and put into place a number of protections."

The report echoes what MSHA will say when it briefs the public on June 29 on its findings, said U.S. Department of Labor solicitor Patricia Smith.

It also offers disturbing details about the conditions in 2.7 miles of active underground mining where air routinely flowed in the wrong direction, if at all. Men were regularly forced to wade through chest-deep water, and the safety inspector who was supposed to file pre-shift reports on air and methane readings did so for weeks before the blast without even turning on his gas detector.

There was so little fresh air flowing to clear away methane, coal dust and other dangerous gases that the normally chilly underground environment grew hot enough to make men sweat.

"It literally felt like you were melting," said roof bolter Michael Ellison, who had called in sick the day of the blast. His shift started at 7 a.m., he told investigators, "and by 8:30, all of us looked like we had been standing out in a rainstorm, just soaking wet."

It was, the report concludes, a mine where the crew could do nothing to save itself when the inevitable happened.

"Everything just went black. It was like sitting in the middle of a hurricane, things flying, hitting you," Tim Blake, one of two survivors, told investigators.

The other, James Woods, was so severely injured he may never be able to talk about what he endured.

Evidence suggests the crew closest to the explosion knew what was about to happen but had little time to react and no way to stop it.

At 2:59 p.m., the operator manually disconnected the cutting machine, a two-step process that investigators say shows he knew something serious was happening.

When dust started billowing from the mine, dispatcher Adam Jenkins frantically called underground, reaching only one crew.

"I hollered and hollered and hollered _ just, you know, praying and hoping that someone would answer me," he told investigators, "and it never happened."

Blake, meanwhile, struggled in the darkness to save his crew, pulling Woods and seven other men from a shuttle car and putting emergency air packs on all but one, whose device was missing.

"They all had pulse," he said.

Blake checked them a few minutes later.

"Everybody had a pulse but one man."

Then he decided to leave them _ "the hardest thing I ever done" _ to get help.

On his way, he met Massey employees who had raced into the mine to help. One was an emergency medical technician, and together in darkness, they prayed.

The report reveals that 19 of the miners died of carbon monoxide poisoning, although several also suffered traumatic injuries in the blast.

Though critics often claim Massey puts production over safety, it's a charge the company vigorously denies.

But the report's narrative delivers a scathing assessment of Massey, saying deviance from the industry's accepted safety standards was the norm.

The report says the mine was a place where foremen improvised on a regular basis to give their crews enough fresh air, where anyone who dared challenge authority was threatened with firing, and where the only thing that mattered was made crystal-clear in a single practice _ calls to the surface with production reports every 30 minutes for company executives.

Although the blast has been widely viewed as a single event, the report says it was actually a chain reaction that lasted from one to three minutes, starting at 3:01 p.m. As coal dust become airborne, it provided more fuel, allowing the blast to continue propagating "like a line of gunpowder," forward in multiple directions, "obliterating everything in its path."

In January, the federal Mine Safety and Health Administration said it suspected the blast began with a spark from the cutting head of a mining machine, which had poorly maintained and plugged water sprayers that failed to douse the flames.

McAteer's investigators agreed.

They also reject Massey's claim that a sudden inundation of methane or natural gas from a floor crack caused the explosion when it overwhelmed all safety systems.

"Evidence found during the investigation does not suggest a force of this magnitude," the report says.

The investigators also concluded the mine's ventilation system had been compromised, in part by flooding in tunnels leading to a fan positioned to suck air through the mine, but also by leaky airlock doors that had been propped open and other missing air controls.

Upper Big Branch was cited 64 times for ventilation violations in 2009.

Massey has spent moths blaming the federal government for the blast, claiming that changes MSHA ordered to its ventilation plan only contributed to the problems.

The independent investigators found no evidence to support those claims.

Nor did they find any records showing Massey complained to MSHA.

The mine about 50 miles south of Charleston hasn't operated since the explosion. Massey has proposed sealing the mine, but details still need to be worked out with MSHA.

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Associated Press reporter Lawrence Messina contributed to this report. Huber reported from Charleston, W.Va.

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Online:

Independent report: http://nttc.edu/ubb/