CHARLESTON, W.Va. – CHARLESTON, W.Va. (AP) — Exploratory teams have found a crack that could have allowed methane gas to pour through the floor of the West Virginia mine where 29 men died in the nation's worst coal mining explosion in 40 years, owner Massey Energy Co. said Tuesday.
The Richmond, Va.-based company also released a 2004 report on two instances when gas poured in through cracks in the floor of the Upper Big Branch mine. Both occurred in different parts of the Raleigh County mine, but near where coal was being extracted with a longwall mining machine, which passes a cutter back and forth along a 1,000-foot-wide portion of the coal seam.
Neither of the earlier episodes resulted in an explosion, according to the report.
The new crack was found last week near the longwall, but teams were unable to check whether it could have been the source of the April 5 blast, Massey said. Spokesman Jeff Gillenwater said he did not know the size of the crack.
"It is too early to determine what role these changes played or to determine the importance of the crack in the mine floor," Massey Chief Executive Don Blankenship said in a statement. "However, this will be a focal point of our investigation and, we hope, the state and federal investigations."
Joe Main, head of the Mine Safety and Health Administration — which wrote the report on the two earlier gas outbursts — said the old reports are only a portion of the agency's investigation.
"While the air quality in the sections of the mine being worked six years ago may provide some insight, the team's primary focus is on the circumstances occurring in the minutes, hours and months leading up to the explosion," Main said in a statement.
The agency is heading the civil investigation of the explosion. The blast also is the subject of a federal criminal probe.
"We know that coal mine explosions are preventable, and we want to learn what caused the deadly explosion at Massey's Upper Big Branch Mine," Main said.
Massey called the report very important, saying it contradicts ventilation changes that MSHA ordered at the mine in the months before the explosion. MSHA had recommended increasing the amount of air flowing along the longwall in 2004. Massey said the agency had required changes in 2009 and 2010 that decreased airflow.
Coal mines rely on circulating vast quantities of air from outside to dilute methane below explosive levels. The gas eventually is blown outside. If there's not enough air, methane can explode or ignite when it's released as coal is cut by mining equipment.
The 2004 report indicates similar outbursts have occurred in southwestern Virginia and at a mine near Upper Big Branch, though none involved explosions. The gas may be coming from reserves 2,500 feet below the mine, which has several active wells on its property, according to MSHA.