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

Authorities evacuated a half-mile area surrounding the Southwest Industrial Gases, Inc. facility and shut down parts nearby Interstates 30 and 35 as the explosions continued for more than half an hour. Video footage showed numerous small fires burning in the area as stacks of gas cylinders exploded.

Three hours after the explosions started, fire crews were hosing down the charred metal wreckage. About a dozen cars in a parking lot and a grassy highway median were damaged.

Fire Department Lt. Joel Lavender said it started around 9:30 a.m. with a malfunctioning connector used to join acetylene tanks during the filling process. He said the three people injured included the manager and a worker at the facility, and a truck driver.

Calls to a phone listing for Southwest Industrial Gases weren't answered.

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

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.

"We are prepared to go into any emergency mode that's needed, but we feel pretty secure here in the jail," Ortiz said.

Jan Malone, a spokeswoman for the Texas Commission on Environmental Quality, said the gases posed no danger to the public. She said Southwest Industrial has been in operation since 1990 and had no violations with the agency. Environmental Protection Agency emergency responders were on the scene, and the U.S. Chemical Safety Board was sending a team of investigators.

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

About 30 buildings near the blasts were without power and would stay that way until fire crews fully extinguished the blaze, said Carol Peters, a spokeswoman for Oncor Electric Delivery.

Vanessa O'Brien said she was standing in a parking lot a few blocks away when she felt at least 20 vibrations from the explosion.

"We felt the whole building move and the windows rattle," she said.