A search and rescue operation is underway for another person who is unaccounted for, while the cause of the explosion is unknown.

An explosion occurred Monday at a steel factory in Clairton, Pennsylvania, authorities said. A spokesperson for Allegheny County said a rescue operation was underway at U.S. Steel Clairton Coke Works for people trapped under the rubble.

One worker died, one person is missing and 10 were injured after an explosion at the U.S. Steel Clairton Coke Works' two baked oven batteries near Pittsburgh.