A total of 204 university students in northwest China's Shaanxi Province have recovered from diarrhea caused by unknown reasons as of Thursday.

The students at the Weishui campus of Chang'an University in Xi'an, the provincial capital, had fallen ill with diarrhea, headache and nausea since late June, sources with the university said.

Most of the cases, scattered across the campus, have recovered shortly after medical treatment. Only 21 are still receiving medical treatment.

At the campus are 17,000 undergraduates.

Leng Lijia, head of the hospital affiliated with Chang'an University, said the illness might be caused by the meals the students had outside the campus in the hot weather.

The local health authorities have ruled out the possibility that the illness were caused by tainted water and food poisoning.

The cause of the illness is under investigation.