The cause of the blast is still unknown. The Pennsylvania plant has racked up fines and faced lawsuits over emissions problems.

The body was discovered after a search operation which stretched into the evening at the US Steel Clairton site outside Pittsburgh. Local police earlier confirmed that one other person had died and 10 others were injured in a large explosion which destroyed part of the plant.

Authorities said their investigation has shifted to the cause of the explosion after they accounted for everyone who was missing.