MORGANTOWN, W.Va. — A crew drilling a natural gas well through an abandoned coal mine in West Virginia's Northern Panhandle hit a pocket of methane gas that ignited, triggering an explosion that burned seven workers, state and company officials said Monday.

The seven workers were taken to West Penn Burn Center in Pittsburgh. Two were released by the end of the day and the others were walking around the hospital and talking with their families.

The explosion happened about 1:30 a.m. in a rural area outside Moundsville, about 55 miles southwest of Pittsburgh. A column of fire shot at least 70 feet high, but the flames fell to 40 feet within hours.

The gas will continue to burn off for two to three days, said Kristi Gittins, spokeswoman for Dallas, Texas-based Chief Oil & Gas.

As it does, a team from Texas-based Wild Well Control, a company that specializes in rig fires, is moving out damaged equipment. Once those workers can safely reach the well, they will cap it, Gittins said.

The fire presents no danger to any structures or people, said Bill Hendershot, an inspector with the state Department of Environmental Protection's Office of Oil and Gas.

The operation was less than a week old when the blast occurred: DEP records show a permit was issued June 2 to AB Resources PA of Brecksville, Ohio.

Gittins said AB Resources is the operator of the well, while Chief has a "participation interest." It is Chief's responsibility to drill and complete the well, she said.