A fatal nitrogen gas leak at a poultry processing plant in Georgia last week occurred as unplanned maintenance was being done on a recently installed processing and freezing line, the U.S. Chemical Safety Board said Monday.
The leak at the Gainesville, Ga., Foundation Food Group plant killed six people, sent 12 others to the hospital, and forced the plant's 130 other workers to evacuate. A release of liquid nitrogen gas pushes out oxygen from the air and makes it unbreathable.
The New York Times, citing a Foundation Food Group spokesperson, reported the accident was the result of a ruptured line carrying liquid nitrogen, which is used to freeze chicken. A representative from the company didn't respond to NPR's request for comment on that report.
Federal officials said they wouldn't speculate on the cause of the leak. They shared new information about the search for answers into the Jan. 28 incident, but cautioned the investigation was incomplete.
Katherine A. Lemos, the CEO and chairwoman of the Chemical Safety Board said during a media briefing of the accident Saturday, "Depending on the complexity of the investigation, it may take up to several years."
Two victims of the leak who were hospitalized have been released. The condition of the third person, who was admitted in critical condition, has improved, the agency reported Monday.
According to Chemical Safety Board investigators, the leak occurred at a production line where chicken is processed, seasoned, and cooked, and then frozen and packaged.
Shortly after entering the plant following the leak, investigators found tools near an immersion freezer, which had major pieces of its system installed between four and six weeks before the leak.
Lemos said a maintenance manager shut off an external isolation valve pumping liquid nitrogen into the processing lines soon after the leak started, likely preventing further damage.
The Chemical Safety Board's does not have the authority to issue fines, citations, or criminally charge anyone or a company at the end of its investigation. Instead, investigators aim to "understand what happened, what led to the event and why it occurred, so that we can recommend changes to prevent future occurrences."
The Occupational Safety and Health Administration is also investigating the leak.