DALLAS -- A series of explosions at a gas facility sent flaming debris raining onto highways and buildings near downtown Dallas on Wednesday and seriously injured at least three people.

A lone Dallas police officer watches explosions as they rise high above the Jefferson Street bridge near Reunion Arena in downtown Dallas, Texas, on July 25, 2007. Explosions followed by black, billowing smoke erupted from a gas plant identified as Southwest Industrial Gasses Inc., injuring two people. [Reuters]

Authorities evacuated a half-mile (0.8 kilometer) area surrounding the Southwest Industrial Gases, Inc. facility and shut down parts nearby Interstates 30 and 35. Video footage showed numerous small fires burning in the area as stacks of gas cylinders caught fire and exploded.

The canisters held acetylene and propane gas, said Texas Commission on Environmental Quality spokeswoman Andrea Morrow. It was not immediately clear what caused them begin exploding around 9:30 a.m.

By noon, fire crews were hosing down the charred metal wreckage to extinguish any lingering flames. Earlier, about a dozen cars burned in a nearby parking lot and a grassy areas of a highway median.

"I thought it was artillery. It was just coming just boom, boom, boom," said witness Tony Love, a former Army soldier.

Parkland Hospital spokesman Robert Behrens said two people injured by the explosions had been brought to his hospital in serious condition. A third man was taken to Methodist Dallas Medical Center, hospital spokeswoman Sandra Minatra said. She did not give out his condition.

According to the industry Web site gasworld.com, Southwest Industrial is a distributor that carries a range of gases, including acetylene, helium and hydrogen, as well as welding equipment. Calls to a phone listing for the company were not answered.

At the edge of the evacuation zone is Dallas County's main jail and criminal courts building, but operations continued there uninterrupted, said Deputy Michael Ortiz of the Dallas County Sheriff's Department.

Carol Peters, a spokeswoman for Oncor Electric Delivery, said about 30 buildings near the blasts were without power and would stay shut off until fire crews extinguished the blaze.