One person has died, one person is unaccounted for and at least 10 are injured following an explosion at a U.S. Steel plant near Pittsburgh, Allegheny County Police Assistant Superintendent Victor Joseph said at a press conference Monday afternoon.

Multiple people have been injured in Pennsylvania, and several medical helicopters have been dispatched to the area.

Two people have died and 10 are injured following an explosion at a Pennsylvania steel plant on Monday, Allegheny County police said.