Preparations for a routine maintenance task may have led to an explosion at a U.S. Steel coal-processing plant near Pittsburgh that left two dead and sent 10 to hospitals, the company said Friday.

U.S. Steel said it developed the information, along with other investigators, from reviewing video footage and interviewing employees. Advertisement

That has suggested to them that the explosion happened when workers were flushing a gas valve in preparation for a routine planned maintenance task, the company said.

The explosion , which heavily damaged part of the sprawling facility, started around a set of ovens where coal is baked to 1,200 degrees Fahrenheit (648.89 Celsius) into a more efficient carbon fuel called coke, a key component in steelmaking. A byproduct of processing the coal i

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