More than 200 people were sickened on Monday by food poisoning in a restaurant in north China's Shanxi Province, local health authorities said.

The sickened customers suffered from nausea, diarrhea and other symptoms after they had lunch at Ruizhou Grand Restaurant in Datong City.Four of the victims were said to be in serious conditions, said a spokesman for the emergency response office with the Shanxi provincial health department.

Some of the sick were receiving treatment at four different hospitals in the city, the spokesman said.

The restaurant served 60 to 70 tables at lunch for two weddings and one birthday celebration on Monday, the final day of the three-day Labor Day holiday in China.

An initial investigation showed that the large number of the eaters falling sick was caused by a food poisoning, but the cause of the food poisoning remained unknown.

A further investigation is underway.