Carbon dioxide from a soda fountain leaked in a McDonald's in Georgia and sickened 10 people, including an woman who later died after being found unconscious in a restroom, police said Wednesday.

Investigators determined a leaky gas line between the walls caused the gas to build up about a week ago to the point where people inside were unable to breathe.

"It caused what is normally a harmless gas to be pumped into the wall cavity and leak into the women's restroom," said Pooler Police Chief Mark Revenew. "At a high level of concentration, it displaces oxygen."

Firefighters were called Sept. 7 to the restaurant in Pooler, about 10 miles west of Savannah, and two women were found unconscious in a restroom. They were later admitted to a Savannah hospital, where eight others from the restaurant were treated and released. Eighty-year-old Anne Felton of Ponte Vedra, Fla., died the next day.

Investigators initially suspected customers fell ill to noxious fumes from cleaning chemicals. An autopsy found no trace of chemicals in Felton, Revenew said, but it indicated she succumbed to asphyxiation.

McDonald's corporate headquarters and the restaurant's franchisees, John and Monique Palmaccio, did not immediately return calls seeking comment.

The police chief said the owners had replaced the soda fountain's gas lines and valves and were allowed to reopen the restaurant.

"At this point we don't anticipate criminal charges," Revenew said. "It just appears to be a mistake."

The U.S. Occupational Health and Safety Administration is also investigating. OSHA investigators were conducting interviews last week, looking into possible workplace safety violations.