An explosion at a U.S. Steel plant near Pittsburgh left two dead and sent at least 10 to hospitals Monday and heavily damaged the sprawling facility, officials said.

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.

Their assessments will look at pollutants like Volatile Organic Compounds, PM2.5 and sulfur dioxide.