ZHENGZHOU - Three animal husbandry heads in central China's Henan Province have been suspended from duty, while other officials were in police custody after pigs tested positive for a chemical poisonous to humans, the provincial government said Friday.

Chiefs of animal husbandry bureaus in Mengzhou City, Qinyang City and Wenxian County received duty suspension notices after 52 pigs tested positive for clenbuterol which is poisonous to humans, said Liu Xuezhou, a member with the provincial food safety leadership group.

Another 27 officials in the province were in police custody, sacked or suspended from duty, said Liu, who is also chief of Henan Provincial Department of Health.

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The province conducted urine tests on 1,512 pigs in nine pig farms, with 52 pigs testing positive. The farms are suspected to have fed food laced with clenbuterol to the pigs.

Also, the province intends to random test more than 1.63 million pigs in five counties and cities.

Liu said meat products containing clenbuterol will be tracked down and stopped from entering the market.

In Nanjing, capital city of Jiangsu Province, 264 pigs at Xingwang Slaughter House were killed and buried after pigs believed to be from Henan's Mengzhou City tested positive for clenbuterol, said Hua Wen, deputy chief of the city's food and drug supervisory bureau.

Authorities randomly picked 20 out of the 264 pigs for urine testes Wednesday, and all tests came back positive.

Hua said 600 kg of pork from a nearby pork market was also destroyed.

Other provinces such as Gansu and Shanxi have strengthened management and monitoring of pig and pork supply chains to prevent clenbuterol-contained products from being sold.

Clenbuterol is a chemical that can be fed to pigs to prevent them from accumulating fat. It is banned as an additive in pig feed in China because it can end up in the flesh of pigs and is poisonous to humans if ingested.