CRESSON, Texas (AP) — Investigators believe a worker dragging his foot along a factory floor sparked a Thursday explosion at a Texas chemical plant that injured two workers and left a third unaccounted for, and fears of another blast amid the toxic chemicals prevented crews from battling the ensuing blaze, an official said. Nine emergency-rescue and fire departments responded to the blaze at the Tri-Chem Industries plant in Cresson, about 50 miles (80 kilometers) southwest of Dallas, but were evacuated from the vicinity because of risk of exposure and of another explosion, Cresson Mayor Bob Cornett told The Associated Press. The worker who dragged his foot while chemicals were being mixed caught fire from the waist up and was airlifted with critical burn injures to a Dallas hospital.Read more on NewsOK.com