Firefighters have decided to let a massive, roaring fire that raged Monday morning at a chemical plant in Waxahachie, Tex. burn itself out, NBC Dallas Fort-Worth reported Tuesday.

Giant plumes of smoke rise from the Magnablend chemical processing plant Monday. (Lara Solt/AP)

The fire is now 80 percent contained, and those people evacuated in the area should be able to return home by 5 p.m.

Officials say they do not know how the fire started, but are launching an investigation to find out.

The Environmental Protection Agency said initial air quality tests show “nothing significant” and said there is no immediate threat to the public.

Photos of the fire:

Waxahachie firefighters battle a massive the fire Monday. (Tom Pennington/GETTY IMAGES)