CHARLESTON, W.Va. -- Teams exploring Massey Energy's Upper Big Branch Mine have found a crack and other damage to the mine floor, evidence that could turn into important clues about what caused the April 5 explosion that killed 29 miners and injured two others, government and company officials said Tuesday.
Massey issued a news release saying a crack had been discovered near the longwall section of the mine and described the crack as among the "potential sources" of methane gas that could have fueled the explosion.
In its prepared statement, Massey linked the crack to incidents in 2003 and 2004 in which methane burst through the floor of the Raleigh County mine, in one instance inundating Upper Big Branch with the explosive gas.
Ron Wooten, director of the state Office of Miners Health, Safety and Training, said his agency was aware of reports that the mine floor had buckled in some places on the "longwall tailgate," a separate set of mine tunnels near the longwall area.
"I had heard that there was some bottom hooving, but I am not aware of any cracks," Wooten said.
Joe Main, assistant labor secretary for the U.S. Mine Safety and Health Administration, refused to answer questions about what floor conditions have been discovered in the mine.
But Main issued a prepared statement that downplayed the importance of any information about the 2003 and 2004 "methane outbursts" at the Upper Big Branch Mine.
"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 the prepared statement.
Teams of state and federal officials, along with Massey representatives, have been exploring the Upper Big Branch Mine over the past two weeks. They are checking to ensure the mine is safe, so investigators can enter to begin gathering physical evidence for the probe of the worst U.S. coal-mining disaster in 40 years.
Investigators believe the deadly blast involved an ignition of methane gas, and was probably made far worse by the buildup of highly explosive coal dust. State and federal agencies are conducting closed-door interviews as part of a civil investigation, and a federal criminal investigation is also underway.
Over the past two weeks, investigators have focused on the 2003 and 2004 "methane outbursts" documented in a pair of MSHA reports.