BEIJING - As a series of food-poisoning cases among students prompted the Ministry of Education to restate its safety requirements for school canteens, several observers said there was nothing inevitable about the mishaps.

"Some people blame increasing food prices for the poor quality of the food, but I think that's wrong," said Chen Chunming, a professor and a retired Ministry of Health official.

"Increasing food prices could make canteens less capable of providing large amounts of food, but not make them provide food that is of so low a quality that it endangers safety."

On Oct 13, the Ministry of Education published an announcement on its website saying that the recent cases of food poisoning have revealed faults in the system used to ensure the food served in schools is safe.

In response, the ministry is now encouraging education officials and schools to place an even greater priority on ensuring that school food is of a high quality, to adopt controls for the purchase, cooking and storage of food and to strictly punish those who are to responsible for food-poisoning cases.

It is also requiring schools to formulate contingency plans to cope with incidents of food poisoning and other public-health emergencies.

Some school officials said they are already doing a lot to ensure that the food served to students is of a high quality. Zhang Zhengfu, a principal at Xinhai Primary School in Zhaotong, Yunnan province, said he and his colleagues use strict management to prevent students from getting sick from eating canteen food.

"For example, we only purchase rice and meat at distributors that have government certifications," Zhang said.

"And to reduce the cost of food that has been pushed up by increasing prices, we buy fresh vegetables from farmers who are close to the school."

The Xinhai school serves children who hail from nearby impoverished places and who cannot afford the cost of meals. Government subsidies are often used to pay for their lunches, which cost barely 3 yuan (50 cents).

"With our short supply of money, our canteen can only supply meat once a week," Zhang said. "But we can still use strict quality control to ensure safety."

Since September, six cases of food poisoning have arisen in Hebei, Jiangxi, Hunan, Guizhou and Shanxi, according to the Ministroy of Education's announcement.

At Zhangjiying middle school in Chengde, Hebei, 135 students contracted diarrhea after they had drunk polluted water on Sept 5. In a more recent case, in Taiyuan, Shanxi province, 197 primary school students contracted a food-borne illness.Then on Sept 13, more than 1,000 parents protested in front of a school gate in Zunyi, Guizhou province, after finding the school canteen was providing rotten vegetables to children, according to the local newspaper Guiyang Evening News.

"Each food poisoning case had different causes, running from improper storage to even the possible economic interests of the purchasers," said Chen Chunming, the professor.

"We cannot say what is the primary cause, but one thing for sure is that we need stricter supervision to cope with the troubles that have been brought about by increasing prices."