Twelve students in Jiangxi province's Wan'an county received hospital treatment on Wednesday after eating school meals suspected of including expired food, according to the local government.

The students displayed symptoms such as stomachaches and were undergoing treatment at two hospitals in the county and nearby Ganzhou. They are said to be in stable condition and improving, the Wan'an publicity department said in a statement released on Thursday.

Wan'an Zhenbaiwei Catering Co, which supplied meals to some primary and middle schools in the county, has been ordered by the county government to suspend operations, and senior executives have been detained for further investigation, the statement said.

A previous joint investigation by the county's market supervision and education authorities had looked into the purchase, storage, processing and distribution of food materials by the company.

Officials in the departments of education, market supervision, agriculture and health are the subjects of disciplinary investigations, the statement said. The county government is also investigating the bidding process that resulted in the company being chosen as a food supplier and will disclose information to the public when appropriate, it said.

The Wan'an county government started the investigations on Monday following recent online posts by netizens that said students at some primary schools, including Shunfeng Primary School and Baoshan Primary School, had stomachaches after eating food at school that had gone bad, and were sent to the hospital.

According to medical records provided by parents, three students were diagnosed with food poisoning and acute gastroenteritis; in the other case food poisoning was suspected but not confirmed, according to a report by Beijing News on Thursday.

Zhenbaiwei Catering had been chosen as the supplier of food for more than 40 middle and primary schools in Wan'an, with services starting on Sept 1, an official from the county's education department told the newspaper.

The department received telephone calls from some parents on Monday voicing concerns about food safety, the newspaper said.

The company did not return calls from China Daily on Thursday.