Explosion at Wacker is second incident within eight days [video]

Clouds billow from the Wacker polysilicon chemical plant after an explosion released a hydrogen chemical gas on Thursday, Sept. 7, 2017, in Charleston, Tenn. The explosion closed the plant, but a statement from Wacker says air quality was unaffected.

An explosion at the Wacker Polysilicon plant closed down nearby roadways for several hours and worried residents in Bradley County on Thursday evening.

It was the second incident at the plant in eight days. This one was caused by a "mechanical incident [that] resulted in a hydrogen chemical release," according to a Wacker news release.

One initial injury was reported. The patient was transported to a hospital by helicopter, but it was not clear whether the person's injury was related to the explosion or if it was because of unrelated cardiac health issues.

A Wacker firefighter was also taken to a local hospital to be treated for heat exhaustion, and seven people were taken to Tennova Healthcare for treatment.