Kurt Knaus, spokesman for the department, said the explosion happened at the R&D Coal Co. anthracite mine in Tremont, Schuylkill County, about 80 miles (130 km) north-west of Philadelphia, and was reported about 10 a.m.
"The mine has been cleared and there are no miners remaining underground," Knaus said. "The cause of the accident has not been determined. We do have both state and federal mine inspectors on the scene and in the mine already.

Copyright Reuters, 2006