St. Joseph, Mo. ? Gas leaking from an open valve provided the fuel for a deadly explosion last month at a pork processing plant under construction, the state fire marshal found in a report released Thursday.

But investigators were unable to conclusively identify what sparked the Oct. 14 blast at Triumph Foods, whose new $130 million plant was nearing completion. The explosion killed one person and injured 14 others.

Possible ignition sources are halogen lighting, fans in the ductwork of the heating system and a striker and torch found in the hallway of the kitchen, the report said.

Damage was limited to the kitchen area, where the uncapped valve was, and an office area. Both were in a building separate from the processing plant.

The report found the open gas valve faced into the grill hood of a stove in the kitchen. The finding was consistent with reports from workers who heard something that sounded like gas flowing into the kitchen area before the blast. The workers also reported hearing a fan running.

Investigator David Miller said he checked the top of the hood for any cap from the valve, but did not find one. He said damage from the blast appeared to be centered in the stove area.

Rick Hoffman, chief executive officer of Triumph Foods, said the report seemed consistent with earlier accounts of the accident.

State officials have estimated the blast caused $5 million in damages. Hoffman said the company is still calculating its own estimate.

James Montee, who represents eight construction workers injured in the accident, said he was working with other attorneys in preparing a lawsuit. The attorneys have not yet determined who will be named as defendants.

“The most obvious question is why is natural gas escaping from a valve into the air and why was it not detected,” Montee said.

Because of the explosion, Triumph has pushed back the date it expects to begin processing hogs to January.