The deadly explosion at Clairton Coke Works near Pittsburgh occurred when a gas valve was flushed before planned maintenance, U.S. Steel said in preliminary findings.

An explosion at a US Steel plant near Pittsburgh, Pennsylvania, left two people dead and at least 10 injured on Monday, heavily damaging the sprawling facility, officials said. One worker was pulled from the wreckage hours after the explosion sent black smoke spiralling into the midday sky in the Mon Valley,