A fire sparked as workers mixed chemicals at a plant south of Dallas. Massive plumes of black smoke and bright orange flames shot into the sky Monday, forcing schoolchildren and residents to evacuate or take cover indoors to avoid possible exposure to dangerous gases.

Flames engulfed a large complex at a Magnablend, Inc., facility in Waxahachie. The fast-moving blaze overwhelmed a sprinkler system and consumed a fire truck, but no injuries were reported from the fire or resulting smoke.

Waxahachie Fire Chief David Hudgins said it wasn’t immediately clear what chemicals were involved in sparking the fire, but crews expected to quell the flames by late afternoon and allow about 1,000 evacuated residents to return to their homes in the city 30 miles south
of Dallas.

“It’s the building that’s burning, and there’s chemicals inside, multiple kinds of chemicals,” Waxahachie Fire Department spokeswoman Amy Hollywood. “Saying which kind would be speculative.”

Nicolas Brescia of the U.S. Environmental Protection Agency said air quality readings in the city of about 25,000 did not require further action but that officials would continue monitoring to ensure hazardous materials did not spread outside the plant.

Magnablend spokesman Donald Golden told WFAA-TV that 25 to 30 employees who were inside the plant’s 100,000-square-foot warehouse evacuated safely when the fire broke out before 11 a.m. Golden said the company manufactures about 200 products, including some that are hazardous when ignited.

Authorities had ordered residents closest to the plant to evacuate, while others were advised to stay inside with doors and windows shut.

Stephanie Otto said she was preparing her new restaurant for a Tuesday opening about a quarter-mile from the plant when she heard sirens and walked outside to see a “huge plume.” She said she could hear what sounded like gun shots for about 15 minutes, and there was a strong smell of ammonia.

“It was huge,” Otto said. “It looked like an atomic bomb went off.”

Ellis County emergency management officials issued a mandatory evacuation order for an apartment complex, an elementary school and a junior college. Sheriff’s officials urged residents not to drive toward the area of the fire.