HAIKOU, Oct. 23 (Xinhua) -- More than 40 teenagers showed symptoms of diarrhea or vomiting at a school in Haikou, capital of south China's Hainan Province, but the source of the malaise remained unknown, local health authorities said on Thursday.

The Hainan Experimental School clinic began receiving diarrhea patients starting from the beginning of this week. By Thursday noon, 43 students, mostly seventh graders, had been sickened, said headmaster Lu Wenke.

Local district health workers collected samples of canteen foodand water from the school on Wednesday to trace the source of the epidemic and to check if poisoning was involved, said Liang Anjin, the Qiongshan District health director.

The tests results would be published in 48 hours, he said.

Most of the teens were given medication and were recovering. Some were brought back home by their parents, Lu said.

District health staff are helping the school clinic doctors to treat students.