Friction between rocks and the metal roof-support system of the Sago Mine — not lightning — probably sparked the methane gas explosion that killed 12 men last year, the United Mine Workers argued Thursday.

The union's report differs from the conclusions of state investigators and the mine's owner that a lightning strike somehow traveled two miles and ignited gas that had accumulated naturally in a mined-out and sealed-off area.

The report lashes out at the federal Mine Safety and Health Administration for what it calls misguided decisions in the months and years preceding the explosion, and accuses it of putting concern about coal companies' profits ahead of miner safety.

The UMW demands the agency "re-establish itself as the government's advocate for miners," prohibit former industry executives from holding the highest offices in the agency and develop a public hearing-style investigation process.

Two previous reports — one by the West Virginia Office of Miners' Health, Safety and Training, one by mine owner International Coal Group Inc. — identified lightning as the most likely cause. A third report, by a former MSHA chief and special adviser to Gov. Joe Manchin, said lightning could not be ruled out.

But the UMW, which participated in the Sago investigation as a legal representative of several workers at the nonunion mine, said the chances of lightning being the cause are "so remote as to be practically impossible."

MSHA has yet to release its own findings about Sago. MSHA director Richard Stickler, a former coal industry executive, said Thursday that his agency shares the union's goal of improving safety and has hired experts to examine the potential causes of the Sago blast.

Atmospheric alarms in the mine sounded at nearly the same instant as a documented lightning strike, at 6:26 a.m. on Jan. 2, 2006. But unlike other coal mine blasts linked to lightning, the UMW says, there was no metal conduit at Sago that could have carried the charge that far.

Rather, the union contends, a spark likely came from rocks banging together or into the network of metal screens, plates and bolts used to hold up a frequently wet and steadily collapsing shale and sandstone roof. Metal rubbing on metal also could have created a spark, the report says.

Decisions by ICG and MSHA in the months and years before the accident created conditions ripe for an explosion, the UMW charges.

The union cited repeated changes to the roof-control plan and a rare practice known as "second mining," in which operators mine coal seams separated vertically by many feet of rock.

At Sago, the process left some areas in the mine more than 18 feet high, which the UMW says is dangerous. It wants second mining banned, saying it increases the risk of roof falls and wall collapses, and that it allows more methane than normal to accumulate.

"It is not factual to say that events beyond the control of the mine operator or the regulatory agencies simply happened," the report says. "The truth is that ICG failed the miners at Sago, and so did our government."

ICG, which is facing lawsuits by families of most of the Sago victims, had not seen and did not immediately comment on the UMW report. But it has previously said the lightning evidence is too strong to ignore, and has taken safety measures aimed at preventing similar explosions.

The union also faults ICG and MSHA for creating and approving faulty ventilation plans that left Sago miners trapped in poisoned air for more than 41 hours, and for allowing sloppy construction of what it contends were substandard seals on the mined-out areas.

One miner was killed in the Jan. 2, 2006, explosion, and 11 others died of carbon-monoxide poisoning as they waited to be rescued. One miner survived.

The report calls on MSHA to take immediate control of rescue and recovery operations, saying ICG took too long to get teams into the mine. It also seeks improvements in safety and communications in underground mines, as well as tougher standards for seals.