Explosion at Clairton Steel Plant Hurts 20

Authorities say at least three of the 20 people hurt in an explosion at a U.S. Steel plant near Pittsburgh were critically injured.

Officials say most of the workers suffered burns, and one suffered chest pains.

Allegheny County Emergency Services Chief Bob Full says the explosion at U.S. Steel's Clairton Coke Works was so powerful it bent steel beams and destroyed block walls.

Union and company officials say the cause of the explosion is being investigated. The Occupational Safety and Health Administration has a team of investigators on site.

The explosion happened during maintenance in the B battery, which consists of 75 ovens. The battery is on the northern side of the plant and was shut down after the explosion, but a U.S. Steel spokeswoman said the rest of the plant was operating normally.