Nearly a year after the Sago Mine disaster that killed 12, state investigators have concluded that the mine explosion was caused by a lightning bolt that ignited methane gas underground, a union official said.
The mine's owner, International Coal Group Inc., has argued since March that lightning was to blame for the Jan. 2 blast, a theory that critics of the company have disputed.
The report is to be released Monday, but United Mine Workers officials who helped in the investigation have been briefed on it, according to Dennis O'Dell, the union's health and safety director.
The chief of the state's mine safety agency did not immediately return a call for comment.
International Coal Group officials declined to comment.
One miner was killed in the blast, and 11 others died of carbon monoxide poisoning in the 40-plus hours it took rescuers to reach them. One trapped miner, Randal McCloy Jr., survived.