Workers were heating coal and preparing for routine maintenance when an explosion rocked a U.S. Steel plant outside Pittsburgh

“It is with profound sadness that I share with you that the U. S. Steel colleague who had been unaccounted for has been located and confirmed deceased, following an extensive search and rescue effort," David Burritt, the company's CEO, said in a statement. At least 10 people were injured in the blast, officials said.

Several people appear to have been injured at a mill in Western Pennsylvania. WPXI reported that emergency crews were sent to an explosion at the U.S. Steel Clairton Coke Works. The mill is located along the Monongahela River south of Pittsburgh.

Timothy Quinn, 39, of East Huntingdon Township, also died in the incident. Ten other people were injured. Three of them are still hospitalized.

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.

Emergency responders are working to free people trapped under rubble at the Allegheny County plant, the Associated Press has reported.