Video shows a huge plume of black smoke above the U.S. Steel Clairton plant after explosions on Monday killed two and injured at least 10. 

The initial explosion sent a column of smoke into the Mon Valley sky surrounding U.S. Steel Clairton Coke Works, which sits along a bend in the Monongahela River south of Pittsburgh. One of the two people who died was identified as 39-year-old Timothy Quinn. The second victim has not been identified as of Monday night. 

A time-lapse video from the Breath Project shows the aftermath of the explosions, though the video does not have sound. Crews were alerted to the plant just before 11 a.m. The cause of the explosions is under investigation. 

Officials said the initial explosion was followed by secondary explosions, which did not cause any "major injuries," Allegheny County said. The explosions rocked homes and rattled nerves across the area.

"All I could see out the window was black smoke," said Deanna Forkey, who manages a business near the plant. "It was very dark." 

"I was sitting in my home office, and I felt my house shake," Glassport resident Sandy Lawson said. 

A firefighter who was among the first crews at the scene on Monday described it as "a bomb went off."

On its website, the Breath Projects says it's a "clearinghouse for information on air quality in Pittsburgh, Southwestern Pennsylvania and beyond." It is a partnership of citizens, environmental advocates, public health professionals and academics.