More than 200 primary school students in Sichuan Province fell ill after an unidentified gas leaked into their classrooms yesterday morning, authorities said.

Primary students receive treatment after possible poisoning by an unidentified gas at a hospital in Yingjing County, Ya'an City, Southwest China's Sichuan Province, June 21, 2007. 208 students were sent to hospitals for checkups, and 21 were reported to be in serious condition. Another 176 were also hospitalized for further observation, Xinhua news agency said.[Xinhua]

Twenty-one were reported to be in serious condition.

The gas leak occurred at the Xinmiao Township Primary School in Ya'an City. Students noticed a foul smell around 9am, and many began experiencing headaches, vomiting and chest pains, said a city government spokesman.

Three ambulances were sent to the school to take sick students and teachers to hospitals, and the county government also offered vehicles.

A total of 208 students were sent to two hospitals for checkups and observation, and 176 were admitted for treatment.

At Xingjing People's Hospital, which had admitted 90 patients by 6pm, the wards were crowded with sick students and their parents late yesterday.

"I smelled something weird at around 9am, and then I felt stomach cramps and got a headache and wanted to vomit," said Li Xiong, a 12-year-old student who was undergoing treatment.

Hospital officials said the students might have inhaled a mixture of carbon monoxide and sulfureted hydrogen leaking from nearby factories.

An electrolytic zinc plant and a lead and zinc plant were ordered to stop production for inspection, a city government spokesman said.