The consumption of offal and meat tainted by clenbuterol can cause dizziness, headaches, hand tremors, palpitations, agitation and other symptoms. The greatest risks are posed to those who have heart troubles, experts said.

"Clenbuterol causes symptoms in several hours," said Chen Junshi, director of the Fortified Food Office under the Chinese Center for Disease Control and Prevention.

"But a small amount won't lead to poisoning. Only ingesting a large amount will."

Until the lab results come back, it will be impossible to know the cause of the food poisoning, he said.

According to a notice from Changsha's publicity department, some residents of Wufeng village, Lianhua town, Yuelu district, suffered from an accelerating heartbeat, vomiting and other discomforts after attending a wedding in the village.

The sufferers were taken to local hospitals for first aid at 8 pm on Saturday.

A China Daily reporter spoke to officials with the provincial department of health, the provincial and city centers for disease control and prevention and the town government on Sunday. But none of them had new information to report about the poisoning.

Phone calls to the city's publicity department were not answered.

Another food poisoning case happened in Yulin city, Shaanxi province, on Friday.

At the Yuhe Central Primary School, in the city's Yuyang district, up to 251 children suffered from nausea, vomiting and other symptoms on Friday morning after drinking milk produced by the Mengniu Dairy Group.