POINT COMFORT, Texas -- Two workers were burned when a plastics plant in Point Comfort exploded into a fireball that lasted for hours Thursday afternoon. The blast forced an evacuation of the facility and residents were asked to shelter in place, KPRC Local 2 reported.

The explosion, which occurred at the Formosa Plastics Plant at about 3:15 p.m., prompted authorities to shut down highways in the area, including the Port Lavaca causeway, state Highway 35 and FM 1593.

The burn victims were taken to the University of Texas Medical Branch in Galveston. Roger Green, 30, was listed in serious condition with burns over 36 percent of his body. John Hunt, 45, is in fair condition with burns on 5 percent of his body.

At least six people received minor injuries, according to Pat Trigg, with Memorial Medical Center in Calhoun County.

Plant officials said the explosion occurred in the olefins 2 unit. The fire burned for nearly six hours, but authorities said there was no threat in the air.

"They can't find any toxicities in the air," Calhoun County Judge Mike Pfiefer said.

"As a precautionary measure, as part of the crisis plan that goes into effect, (nearby residents) have been asked to shelter in place until we can determine that there's no hazards taking place," plant spokesman Roy Thibault said.

Residents 10 miles away heard the explosion.

"We just heard it rumbling and then all of a sudden, it just blew up. It was very upsetting," resident Helen Smith said. "It's just big black smoke over there."

The Texas Commission on Environmental Quality said there were three explosions at the facility. The air will be closely monitored, officials said.

The Occupational Safety and Health Administration planned to investigate, agency spokeswoman Diana Petterson said. The cause of the blast is not yet known.

The plant, which has 1,600 full-time employees and 400 contract workers, is located 26 miles southeast of Victoria, Texas, on the coast. The 1,800-acre complex has eight plants.

"The plant makes a number of different type of plastic resin. In addition to PVC, they make polypropylene and polyethylene, which can be used in milk bottles and soda bottles," Thibault said.

Point Comfort has less than 1,000 residents.

Formosa Plastics Corp. USA, based in Livingston, N.J., is a privately held plastics and petrochemicals company formed in 1978. In additional to Port Comfort, it has facilities in Delaware City, Del., Illiopolis, Ill., and Baton Rouge, La.

Shelter-In-Place Order

When a shelter-in-place order is issued, residents should:

Go inside.
Shut all doors and windows.
Turn off air conditioners and heaters to prevent outside air from getting inside.
Stay off the phone.
Do not use fireplaces. Put out fires and close all dampers.
Move to a room with the fewest windows and doors. Tape around doors, windows, exhaust fans and vents using plastic sheeting or garbage bags, if directed.
Turn on the radio or television to listen for further instructions.

Families are advised to have the following items in a shelter-in-place kit:

Two rolls of duct tape
Cloth and paper towels
Plastic sheets or trash bags
Flashlight and extra batteries
Battery-powered radio
Two gallons of water
Nonperishable foods

If your eyes, nose or throat become irritated, protect your breathing by covering your mouth with a damp cloth, take frequent, shallow breaths and stay calm.