This allegation comes after over 300 people had to be taken to hospital when they ate pork containing clenbuterol.
Local media reported the illegally practice of feeding pigs clenbuterol is a popular on many pig farms of East China's Zhejiang, providing about 10% of all pork products sold in Shanghai.
Driven by high profits, farmers feed small amounts of the drug to pigs in the hope that it will greatly improve their muscle ratio and shorten the growing period, despite a governmental ban, as the chemical causes nervous and cardiovascular damage to people.
It is an open secret that if farmers stop using the chemical several weeks before the pigs are slaughtered, it is hard to be detected.
Food authorities have traced the source of the contaminated pork to a batch of pigs provided by two pig farms located in the neighbouring cities of Jiashan and Jiaxing, and have banned pig trading from the two places.
But the exact number of poisoned pigs and why these products with healthy certificates are in the system remains a mystery. So far, one merchant has been detained and interviewed by the police.
Up until now, since September 13, Shanghai medical centres have reported 336 people poisoned by the bad-quality pork. All the patients have now left hospital.
