CHARLESTON, W.Va. -- Federal agents are interviewing current and former Massey Energy employees as part of a sprawling criminal investigation into the April 5 explosion that killed 29 miners at the company's Upper Big Branch Mine in Raleigh County, according to sources familiar with the inquiry.
Officials from the U.S. Attorney's Office, the FBI and special investigators from the U.S. Mine Safety and Health Administration have been conducting the interviews.
Federal and state sources discussed the interviews on the condition that they not be named, because they were not authorized to talk about the criminal investigation.
U.S. Attorney Chuck Miller in Charleston referred all questions about the matter to Department of Justice officials in Washington, who declined official comment.
Investigators are focused on finding out if any criminal violations of mandatory health and safety standards for underground coal mines were committed that might have been involved in causing the explosion.
Such violations are misdemeanors, while any faking of required mine safety-check records or other safety documents required by MSHA is a felony.
Massey issued a statement that referred to "unsubstantiated rumors" of a criminal investigation and said Massey "has no knowledge of criminal wrongdoing."
"It is not uncommon that an accident of the size and scope of UBB would lead to a comprehensive investigation by relevant enforcement agencies," the Massey statement said. "We are cooperating with all agencies that are investigating the tragedy at UBB. Massey does not and will not tolerate any improper or illegal conduct and will respond aggressively as circumstances warrant."
Investigators believe the huge explosion was caused by the ignition of methane and probably made far worse by accumulations of coal dust.
Federal and state officials have delayed going back underground to gather evidence because sampling has found gases that could indicate there is an ongoing fire. Massey is pumping nitrogen into the mine to put out the fire, but officials have said privately it could be several months before it is safe for teams to re-enter the mine.
Formal interviews for the civil investigation by MSHA, the state Office of Miners Health, Safety and Training -- as well as special state investigator Davitt McAteer -- also have been on hold for weeks.