GARNER, N.C. – A gas leak caused the deadly explosion last week at ConAgra Foods’ Garner, N.C. meat plant, said Phil Durham, special agent in charge of the Bureau of Alcohol, Tobacco, Firearms and Explosives National Response Team, during an A.T.F. press conference.

The team tracked gas lines to pump room #2 and a natural gas leak was discovered, according to Garner News. The Garner plant was recently upgrading from a steam system to a gas hot-water system. The Occupational Safety and Health Administration and the U.S. Chemical Safety Board will now lead the investigation to determine how the natural gas ignited.

Several plant employees said they smelled gas on the morning of the explosion, Mr. Durham said, but he added he did not know if they notified supervisors about the smell.

"ConAgra Foods expresses its thanks to A.T.F. and all agencies for their support and quick response to the investigation into the June 9 accident at the company’s Garner, N.C., plant," ConAgra Foods said in a statement sent to "We appreciate A.T.F.'s swift determination to eliminate criminal activity. We continue to provide our full support to the authorities, including O.S.H.A., the U.S. Chemical Safety Board and the Wake County Fire Department, as they investigate the cause of the accident and bring the investigation to conclusion."