BEIJING -- More than 200 students from a primary school in southwest China were hospitalized for food poisoning during the weekend, the Xinhua news agency said on Monday.

Provincial authorities have sent a team to investigate the cause of the poisoning, Xinhua said, adding that none of the cases was life-threatening.

Food poisonings are a frequent problem at Chinese schools, especially in rural areas, where lax official supervision encourages canteen contractors to cut costs at the expense of proper hygiene conditions and food safety.

Of 185 food poisoning cases reported in China from April to June, about a quarter involved school canteens that had made 1,400 people ill, according to the Health Ministry.

In the latest case, Xinhua said, children from the Experimental Primary School in Chongzhou city in Sichuan province filled three floors of a local hospital.

"The pupils had a lunch in the school on Friday but developed symptoms of food poisoning from Saturday night and Sunday," it said, adding that the symptoms of headache, fever, diarrhea and vomiting were moderate.

In April, 112 students fell ill after a lunch at their primary school in the southwestern province of Yunnan.

The biggest case in recent years occurred in 2003 when a soy drink promoted by local education authorities poisoned some 3,000 pupils, killing at least one in the northeastern province of Liaoning.