The cause of a food poisoning which left 186 villagers ill in northwest China's Gansu Province has been traced to tainted spices in snack foods, the Center of Disease Control and Prevention in Lanzhou, the provincial capital, said on Thursday.

The food poisoning, which was reported on April 29 in three villages in Yuzhong County, was caused by D-group salmonella, a sort of intestinal bacteria, according to the center's test report.

Fifty-five of the 186 people affected were hospitalized, but all had been discharged by Tuesday.

According to health authorities of Yuzhong County, the villagers became ill after they had eaten niangpi sold by a vendor from Lanzhou.

Police have arrested the vendor, surnamed Tie.

Niangpi, a traditional steamed snack made from wheat, is popular in northwest China, including Gansu and Qinghai.

(Xinhua News Agency May 7, 2009)