Students receive transfusions at a hospital in Sichuan. [Photo from weibo.com]

Hundreds of students at a middle school named Yingtian School in Meishan city of Southwest China's Sichuan province displayed unexpected symptoms of fever, tiredness, vomiting and dizziness on Thursday, according to scol.com.cn, a local news website.

As of 2:12 pm on Friday, a total of 346 students were sent to the hospital, among whom 216 were hospitalized, with 45 in serious condition. The rest are still at the hospital for observation.

The cause of the group illness is still being investigated.