A fire at a Texas chemical plant Thursday injured two workers and left a third unaccounted for, and fire crews weren't able to battle the blaze because of the toxic fumes being spewed into the air, an official said. Investigators believe the fire at the Tri-Chem Industries plant in Cresson was sparked by a worker dragging his foot on the floor while chemicals were being mixed, said Bob Cornett, the mayor of Cresson. He said that worker caught fire from the waist up and was airlifted with critical burn injures to a hospital in Dallas, which is about 50 miles to the northeast. Another worker with less severe injuries was treated at a hospital and a third worker is missing. Cornett identified the missing worker as 27-year-old Dillon Mitchell. Nine emergency-rescue and fire departments responded to the blaze but were evacuated from the vicinity because of the chemicals' toxicity and fears of another explosion, the mayor told The Associated Press. Cornett said Tri-Chem Industries mixes chemicals that are primarily used by the oil and gas industry to drill disposal wells, and that although he didn't know how many of the chemicals at the plant were hazardous, "what was burnt and exploded was quite toxic." The Environmental Protection Agency deployed an on-site coordinator to help monitor air emissions, according to spokesman David Gray. Cornett said that the wind was carrying black smoke and fumes emanating from the plant away from residents, but that the city could issue an evacuation order if the wind direction changed. A spokesman for the Texas Commission on Environmental Quality, the state agency responsible for coordinating the cleanup, declined to produce a list of the plant's on-site chemicals, telling an AP reporter to file a public information request.