Several nearby houses caught fire but there were no reports of injuries, and Airgas Mid South said it had accounted for all 75 employees who may have been working at the plant at the time.
The fire apparently started in a storage facility for industrial gases, said company president Mike Duvall.
``We don't know how or why at this point,'' he said.
The facility stores high-pressure steel cylinders containing acetylene, propane, oxygen, argon, nitrogen and carbon dioxide, Duvall said.
The canisters exploded in a violent cacophony for more than two hours, sending projectiles as high as 300 feet and up to a half-mile away. After some 100 explosions, Fire Capt. Hubert Rouse said his crews managed to get close enough to control the fire.
For a time, roiling black clouds of smoke shut down traffic on Interstate 244.
Authorities evacuated a three-quarter-mile radius.
``We're not exactly sure what's burning,'' Rouse said. ``We treat all smoke as toxic. The evacuation is about the debris and smoke.''
An Airgas facility in Sacramento, Calif., caught fire last month, also producing dark smoke that prompted evacuation of nearby homes.
Airgas Mid South is headquartered in Tulsa and has locations in seven other states in the region. Parent company Airgas Inc. is in Radnor, Pa.
