The federal Mine Safety and Health Administration has formally begun its probe of last week's deadly wall collapse at a Tri-Star Mining strip mine in Barton, Md.

Agency spokesman Dirk Fillpot said the investigation is focusing on the cause of the accident and mine compliance with safety standards. He said investigators will examine the accident scene, interview mine employees, review records and inspect equipment.

The collapse killed two miners, 38-year-old Mike Wilt of Frostburg and 51-year-old Dale Jones of Lonaconing. Both were operating heavy machines when the 125-foot wall collapsed and buried them under tons of dirt and rocks.