A seven-year-old boy died and 55 others fell violently ill after eating poisonous beef in south China's Yunnan Province, local government sources said Saturday.

The incident happened around 5:00 PM Thursday in Zhadian Town, Gejiu City of Honghe Autonomous Prefecture, an area mainly populated by people from the Hani and Yi ethnic groups.

The victims ate stewed beef sold by a street vendor in front of an apartment complex beside a local smelting factory, said Xie Xinying, an official with the provincial health department.

She said the city health bureau started to receive reports around 7:00 PM Thursday that many people felt nauseous and had headaches after eating the beef.

A seven-year-old boy named Kong Shanshan showed symptoms of poisoning about ten minutes after eating the beef. His family thought it was a digestion problem, and used the traditional Gua Sha method -- which involves pressuring the skin to produce red spots and promote blood circulation -- to treat him. The boy died after being taken to the village clinic, Xie said.

Fifty-five people were taken to several local hospitals including the Fifth Hospital Affiliated with the Kunming Medical College and the Prefecture's Third People's Hospital, she said.

About a third of them have since returned home and the rest are in a stable condition, she said.

Most of the people who fell ill were factory staff and their families and the rest were migrant workers in the town.

Police later arrested the beef vendor surnamed Li. He said he ran out of salt when he was cooking beef at home, and grabbed something which looked like salt and added it to the beef.

Sample tests show more than 12 grams of nitrite per kilogram of beef, four times the fatal amount, Xie said.

"The local authorities need to learn a lesson here, and step up food safety inspections," she said.

Nitrite is used in very small quantities as a food additive. High amounts can lead to headaches, vomiting, unconsciousness and even death.

On Wednesday, more than 50 children in a private kindergarten in Zhengzhou, capital of Henan Province were poisoned after drinking undercooked soybean milk. Some of them are still in hospital.

The person in charge of the private kindergarten and three cooks who prepared the breakfast have been detained by police.

China's State Council, the cabinet, issued a circular on Monday requiring government departments and businesses to enhance food safety checks during the upcoming weeklong May Day holiday.

(Xinhua News Agency April 29, 2007)