As for what caused the blast, answers remain elusive. Investigators have not yet entered the mine. Conditions underground are still too hazardous. On an investor conference call Thursday, Massey officials said their crews were still trying to make the mine safe enough for federal, state, and company investigators to get inside.
Board members began their call with a moment of silence for the miners who died.
"The Massey Energy family continues to grieve for those lost in the awful tragedy at Upper Big Branch and remains fully committed to the safety of our members," the company's public statement said.