Pooler Fire Chief Wade Simmons told reporters that the incident occurred about Wednesday noon when they were called out to the McDonald`s to deal with a medical emergency.
Firefighters entered the women`s rest room at the restaurant where the sickened people were found. Stricken by the odor, they immediately backed out and put on their breathing apparatus before re-entering the room, Simmons said.
Nine people, including three firefighters, were taken to hospital. Among them, Anne Felton of Ponte Vedra, Florida, died early Thursday.
Authorities did not give details about the cause of the incident or nature of the toxic fumes, saying autopsy will be performed to truly understand what had happened.
John and Monique Palmaccio, the owners of the McDonald`s franchise, said in a statement Thursday afternoon that the authorities have been unable to determine the cause of this incident.
"After their thorough on-site investigation, the restaurant was deemed to be safe and reopened on Wednesday afternoon," said the statement. "We continue to work with the local authorities to collect more information about what may have happened."