Mainland police have detained at least 22 people after a television expose about illegal additives in pig feed.
The detainees included 14 people from Henan - seven pig farm managers, six traders and one buyer for Jiyuan Shuanghui, a subsidiary of the mainland's biggest meat processor. Eight others were taken into custody in Nanjing, Jiangsu province, where a slaughterhouse handled some of the contaminated animals, Xinhua reported.
The suspects were detained after national broadcaster China Central Television aired a report on Tuesday about pigs testing positive for clenbuterol hydrochloride, known in China as 'lean meat powder'.
The additive makes pigs produce leaner meat but is toxic to humans. It is a criminal offence on the mainland to feed it to livestock or sell and process animals fed with it.
The CCTV report said some farmers in Jiyuan, Mengzhou and Qinyang in Henan put the banned additive in pig feed and bribed local livestock inspectors to turn a blind eye to the practice.
The contaminated pigs were transported across the provincial border and sold in Nanjing. Some of the pork was also sold to the Jiyuan subsidiary of the Shuanghui Group.
The revelations are yet another blow to the mainland's scandal-prone food industry. In 2008 at least six children died and nearly 300,000 were made ill by baby formula laced with melamine, an industrial compound added to simulate high protein levels.
Despite repeated government crackdowns, toxic milk powder has repeatedly surfaced on the mainland in the past two years.
In February, the US Food and Drug Administration refused imports of four food products from mainland companies after detecting melamine in them.
In Henan, the pig feed scandal has sent the provincial government into crisis mode. At least six officials and employees at lower-level animal inspection stations have been fired or suspended, including the chiefs of livestock bureaus in Mengzhou, Qinyang and Wen county, who were suspended from duty.
The Henan Food Safety Office told Xinhua that provincial authorities had isolated and tested 1,512 pigs from nine farms that were allegedly fed with the banned additive, and traces of the substance were detected in 52 of the animals.
The authorities were preparing to conduct random tests on 1.63 million pigs from the five counties mentioned in the CCTV report. The government was also investigating more than 1,300 pig farms and 130 feed and veterinary suppliers, Xinhua said.
All meat products suspected of contamination had been removed from shop shelves and all tainted feed and meat destroyed.
Meanwhile, at Jiyuan Shuanghui's processing facilities, of the 689 pigs awaiting slaughter, 19 tested positive for clenbuterol.
Shuanghui, which counts Goldman Sachs among its investors, has shut down the Jiyuan branch affected by the contamination so it can conduct its own inspection.
On Thursday night, the Shuanghui Group posted a statement on its website, ordering Jiyuan Shuanghui to recall its products from the market and destroy them under government supervision to dispel public concerns about food safety.
Four executives at the Jiyuan branch had been sacked, the statement said. The group also promised to step up oversight at all its plants.
The government is investigating 130 feed and veterinary suppliers
And officials are investigating the activities at more than this number of pig farms: 1,300
Mainland health authorities are about to conduct tests for clenbuterol hydrochloride in this number of pigs: 1.63m