By Paul J. Weber
The Associated Press

DALLAS — Federal investigators said Thursday there are similarities between a series of fiery blasts at a downtown gas facility and explosions at a St. Louis plant in 2005 that sent cylinders shooting into a residential neighborhood.

Sidestepping dozens of mangled acetylene tanks and burned-out cars, the U.S. Chemical Safety and Hazard Investigation Board began its probe into Wednesday's explosions that rattled buildings several blocks away and shot flaming debris onto busy highways.

The chain reaction of exploding tanks at Southwest Industrial Gases Inc. injured three people, two of whom remain hospitalized. The scene reminded CSB investigators of explosions at the Praxair Inc. plant in St. Louis where thousands of cylinders caught fire, some shooting like missiles into the sky.

"The incidents are very similar in the way they rapidly cascaded in a domino effect, spreading from cylinder to cylinder until you had an enormous fire that was overwhelming," said Robert Hall, the agency's lead investigator.

Hall, who was also led the federal probe into the Praxair explosions, said it may take a year before the agency's review of the Dallas site is complete.

Messages left for Virginia DuPuy, a co-owner of the Southwest facility, were returned by an employee who said she would not be available for comment. DuPuy is also the mayor of Waco, about 100 miles south of Dallas.

Authorities said the fire began when a connector used to join acetylene tanks during the filling process malfunctioned. Two employees tried keeping the cylinders cool with a fire hose but the canisters erupted anyway.

Daniel McMurry, 56, a co-owner of the plant, and Randall Bibb, 50, were burned in the blasts. Parkland Hospital reported Bibb in serious condition Thursday, with McMurry listed as fair.

The CSB, which has no regulatory authority, issued a safety bulletin recommending several steps for gas storage companies after its Praxair investigation. Those suggestions included fire protection systems to cool cylinders and adding barriers to contain explosions.

On June 24, 2005 in St. Louis, one propylene cylinder stored on asphalt caught fire — probably due to static electricity, the CSB report said — and the blaze spread to propane and acetylene cylinders. Eventually, more than 8,000 cylinders caught fire, and one large fireball after another blasted into the sky.

Hall said it is too early to determine whether Southwest may have used the agency's recommendations. At the charred Southwest site Thursday, burned and broken cylinders remained stacked together.

The explosions set off bursts of flames and a billowing stack of black smoke that could be seen for miles. Authorities evacuated a half-mile area and shut down portions of Interstates 30 and 35, where flaming debris ignited small grass fires next to the roads.

Dallas Assistant Fire Chief Debra Carlin said the department had not inspected the facility since 2002. But she said even a more recent inspection would not have been relevant because the fire was the result of an equipment failure that was not an integral part of the building.

Carlin said the only violations she has immediately found date to the 1990s, when the plant was cited for "minor" violations like failing to secure gas cylinders to keep them from falling.

"I don't have any reason to believe that it wasn't (safe)," Carlin said.

Two canisters propelled like rockets across the interstate and struck Reunion Arena, the former home of the Dallas Mavericks and Dallas Stars, said Kenny Shaw, the city's director of emergency management.

"I'd call it a significant event," Shaw said. "It's impressive that we didn't have more injuries, or even deaths."