Two methane monitors were recently removed from the longwall mining machine — one of the potential sources of the blast — along with a data recorder that functions like an airplane's black box, said Kevin Stricklin, safety chief for the federal Mine Safety and Health Administration.
The devices will be inspected Saturday at an MSHA facility in Triadelphia, he said. Together, they could tell investigators whether employees of Virginia-based Massey Energy tampered with methane monitors designed to sound alarms and shut off equipment when explosive gases reach dangerous levels.
Massey has repeatedly denied the monitors were shut off and met with families Monday to reassert that claim.
But state mine safety chief Ron Wooten said investigators don't have enough information to reach a conclusion yet, and special investigator J. Davitt McAteer called Massey's statement premature.
Former Massey employees have told National Public Radio it was common to disable methane detectors so the mining machines would keep running when pockets of methane were encountered.
There are several ways to disable methane monitors, including bridging them out electrically, Stricklin said. Sensors could also be covered with plastic bags or moved to a location where they would not easily read gas. The monitors can also be recalibrated to avoid shutting down machinery, he said.
Wooten said the data recorder contains six days' worth of information that should indicate when the longwall was cutting and shut down, among other things.
State Office of Miners' Health Safety and Training spokeswoman Leslie Fitzwater said Thursday that a meeting will be held Tuesday night at MSHA's mining academy in Beaver to update families on the investigation.
"They're not going to address any specific issues," Fitzwater said.
At least two families said Thursday they had no knowledge of the meeting and may not be able to share information if they do attend.
Clay Mullins, whose brother Rex Mullins died in the mine, said MSHA has asked the families not to share information.
"They're very careful in what they tell us because they don't want to do anything to hurt their investigation or the FBI's investigation," he said.
MSHA spokeswoman Amy Louviere said Thursday her agency "can't and wouldn't" prohibit families from speaking to the media.