Pupils receive medical treatment in a hospital in Xinhua county, Central China's Hunan province on Sept 13, 2013. [Photo/CFP]

CHANGSHA -- As of Friday afternoon, 180 pupils in Central China's Hunan province had been hospitalized after showing adverse symptoms after having meals at school, local authorities said on Saturday.

Pupils from some elementary schools in Xinhua county have headaches, stomachache and have been vomiting since Sept 10.

The pupils began to show those symptoms after they had milk and cookies at local schools. The students have been sent to local hospitals for treatment.

As of Friday afternoon, 168 students had been discharged from hospital, while 12 remain for further observation, the county government said.

The milk and cookies supplied to the students have been sealed and samples have been sent to the provincial disease control and prevention center for investigation.

Preliminary investigation shows that milk might have caused the incident, according to the county government. Further investigation is under way.