St Joseph, Mo. ? A task force of local, state and federal investigators converged on the Triumph Foods plant Thursday to begin determining what caused an explosion that killed one construction worker and injured 14 others.

Police, fire and building code officials, as well as representatives of the Occupational Health and Safety Administration and the Division of Alcohol, Tobacco, Firearms and Explosions, met Thursday with company officials, who had planned to open the pork processing plant later this fall.

The group also plans to talk to Missouri Gas Energy, which supplies the plant, and the construction contractor, Epstein Co.

While initial reports suggested the blast was caused when a welding torch ignited a natural gas line, authorities have declined to assess any blame until after the investigation is completed.

The explosion, which was felt a quarter-mile away, blew out a dozen windows on the front of the plant, tossing some contractors onto the front lawn. It caused part of the second floor to collapse, pinning other workers under the rubble. Firefighters said the blast originated in an area of the building that holds offices and a cafeteria.

One man, Andrew Bauer, 21, of Stewartsville, was killed. Two of the 14 injured are still listed as critical, said Marcy George, a spokeswoman for Heartland Regional Medical Center in St. Joseph. Seven of the 14 had been treated and released, with two listed as fair and three stable Thursday afternoon.

Police spokesman Cmdr. Jim Connors said authorities won’t release the workers’ names until after investigators have interviewed them.

Triumph Foods remained mum on the explosion. A woman who answered the phone at the company’s temporary headquarters in St. Joseph said Triumph had no comment and wouldn’t give her name.

David Eaheart, marketing director for Merriam, Kan.-based Seaboard Corp., which plans to market pork produced from the plant, said it hadn’t had a chance to talk with Triumph officials and didn’t know how much the incident will push back the plant’s opening, which had been scheduled for some time in November.

Triumph Foods is owned by more than 40 pork producers throughout the Midwest.

The $130 million plant is considered a huge economic development boost for St. Joseph and is expected to employ 1,000 workers.