A major fire has engulfed an industrial plant in the U.S. state of Texas, sending large plumes of potentially toxic smoke into the sky.

The fire broke out Monday at a chemical plant south of Dallas. Local authorities said all workers had evacuated. They appealed to neighboring communities for additional firefighters to help battle the blaze, which was burning out of control.

Authorities evacuated several buildings near the plant, including a college and an elementary school. It was not clear what chemicals and gases were pouring from the site.

The plant's operator, Magnablend, Inc., says it makes custom chemicals for a variety of industries, including oil fields, agriculture, construction and industrial cleaning. The company had no immediate comment on the fire.