Washington, April 6 (Inditop.com) An explosion at a coal mine in the US state of West Virginia killed six miners Monday.

Ron Wooten, director of West Virginia Office of Miners’ Health Safety and Training, told media that six miners were dead and 21 were missing following an explosion at Upper Big Branch mine in Raleigh County, an underground mine operated by Massey Energy subsidiary Performance Coal, Xinhua reported.

The mine is located bout 50 km south of Charleston, capital of West Virginia.

Wooten said the explosion occurred at about 3 p.m. Monday. Massey Energy didn’t immediately provide further details with regard to the casualties, extent of damage or if there were people trapped inside, saying those numbers are “uncertain” at the time.

Local TV WCHS said dozens of miners are believed to be trapped underground. Emergency crews from Massey Energy, the State and federal agencies are responding to the incident.

Massey Energy, the fourth largest coal producer in the US according to revenue, operates 35 underground and 12 surface mines in West Virginia, Kentucky and Virginia, according to the company website.