Officials are investigating the cause of a Pennsylvania steel plant explosion that killed 2

Officials are investigating the cause of a Pennsylvania steel plant explosion that killed 2 Updated 12 mins ago Officials are working to determine the cause of an explosion that rocked a steel plant outside Pittsburgh, leaving two dead and 10 injured. The blast occurred Monday at the Clairton plant in the Mon Valley. Emergency services say a fire started late morning, and a rescue effort continued into the night. The plant is still partially operational. Allegheny Health Network treated seven patients, discharging five. The rumbling from the explosion, and several smaller blasts that followed, was felt through the community about 15 miles southeast of Pittsburgh. U.S. Steel, now part of Nippon Steel, has promised a full investigation.