HARRISBURG, Pa. (AP) — Preparations for a routine maintenance task may have led to an explosion at a U.S. Steel coal-processing plant near Pittsburgh that left two dead and sent 10 to hospitals, the company said Friday.

Ten people were hospitalized after the blast at a coke plant in Clairton, Pa., near Pittsburgh. One person who had been missing was found dead late on Monday.

The explosion, followed by several smaller blasts, could be felt in the nearby community and prompted county officials to warn residents to stay away from the scene so emergency workers could respond.

An explosion at a U.S. Steel plant near Pittsburgh left one person dead and sent at least 10 to hospitals Monday and heavily damaged the sprawling facilty, with emergency workers still searching the badly charred rubble for a missing worker,

The chief of the Allegheny County Emergency Management recounted for reporters the conditions inside the Clairton Coke Works plant following Monday's explosion.

United States Steel said on Friday a fatal blast that killed two and injured 10 others at its Clairton Coke Works plant near Pittsburgh happened when flushing a gas valve, ahead of scheduled maintenance.