CHANGSHA, July 8 -- Sixty people were sent for medical observation on Tuesday after a suspected mass food poisoning in central China's Hengyang City.

Since Monday afternoon, dozens of people have developed symptoms of stomach aches, vomiting and diarrhea after attending a dinner party at a village in Hengnan County, according to the county government.

As of Tuesday afternoon, 49 of them have been discharged from hospital and 11 remain under observation.

Local government authorities are investigating the incident.

They have already ruled out the possibilities of deliberate poisoning and epidemic outbreak, according to the county government.