A suspected food poisoning case in southwest China's Yunnan Province which left one dead and three in critical condition in late February was caused by a disease caused by parasites, local authorities said on Thursday.

An examination of water, blood and urine samples from the nine victims proved that they contracted trichinosis, a disease caused by parasites after eating raw or undercooked pork, said Yang Jun, vice director of the provincial disease prevention and control center.

The incubation period of the trichinosis disease depends on the number of parasites in the meat and the amount eaten. It can range from five to 45 days but it is usually 10 to 14 days.

A suspected food poisoning case occurred at a construction site near Biyuhe Village in Lanping County on February 18. Nine workers developed symptoms of numbness of limbs, dizziness, fever, diarrhea and vomiting on February 21, and one worker died on February 26.

"At the construction site, we saw workers cooking with one single chopping block, and they cut both raw vegetables and meat on it. The problem might lie in the undercooked food," Yang said.

The patients are taking antiscolic pills and are recovering, he said.

(Xinhua News Agency March 5, 2009)