By AUDREY McAVOY, The Associated Press

An explosion at a U.S. Steel plant south of Pittsburgh killed two people and injured 10 others . The CEO has vowed to find out what caused Monday’s blast, while union officials say representatives will work to ensure a thorough investigation.

The plant, Clairton Coke Works , is one of four major plants in Pennsylvania owned by U.S. Steel, an icon of the domestic steel industry and American industrialization for over a century. The plant is in the Mon Valley, a region of the state synonymous with steel.

Here’s what to know about the explosion:

Blast felt nearby

Allegheny County Emergency Services said a fire at the plant started around 10:50 a.m. The explosion, which was followed by several smaller blasts, sent black smoke spiraling into the

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