One showed a switch that requires an operator to push a button while changing it. "The explosion could not have possibly thrown that,'' Blankenship said. "This shows the water valve which also had been cut off, which shows that they had again shut down the wall.''
Federal Mine Safety and Health Administration officials have not dismissed the possibility that methane flooded the mine through a crack. But the agency has said the crack identified repeatedly by Massey was not the source of gas in the mine that day.
MSHA hasn't determined what caused the explosion, but a preliminary report issued in April identified methane fueled by coal dust was responsible.
On Friday, the agency released information that 1,400 of 1,803 samples collected inside the mine by investigators show excessive amounts of coal dust were present before the blast. Massey disputes that evidence, noting that a federal administrative law judge dismissed citations based on similar samples after a 2001 explosion in Alabama.
The Associated Press reported Sept. 12 that handwritten logs recording inspections by Upper Big Branch employees showed eight conveyer belts had excessive amounts of coal dust 32 minutes before the explosion.
Massey officials insist the mine was properly dusted at the time of the blast.
MSHA, however, announced an emergency rule Tuesday to require underground mines to do more to control coal dust.