Authorities in central China detained three officials and launched a probe into hundreds of pig farms on Friday after animals there tested positive for a banned chemical that can be dangerous to humans.
The latest food safety scandal in China emerged as the official Xinhua news agency said it had found that 52 out of about 1,500 pigs in nine farms in Henan province had tested positive for clenbuterol, a drug used by farmers to bulk up livestock.
The report prompted supermarkets to pull from the shelves Shineway brand meat products belonging to the country's largest meat processor, Henan Shuanghui Investment and Development Co.
The government said it would continue to probe more than 1,300 pig farms and 130 feed and veterinary drugstores.
Police had detained seven pig farm managers, six brokers, and a Henan Shanghui buyer as part of the investigations, Xinhua reported.
Shenzhen-listed Henan Shuanghui Investment and Development said in a statement this week that it had halted operations at one of its subsidiaries, Jiyuan Shuanghui, while authorities investigated the case.
Parent company Shuanghui Group expressed a "deep apology for the incident in the unit, which had troubled consumers" in a separate statement.
The scandal is the latest in a string of blows to China's food safety reputation.
In 2008, the industrial chemical melamine was found to have been added to infant powdered milk, killing at least four babies and sickening thousands.
A further six officials and workers at animal quarantine stations had been sacked or suspended as part of the Jiyuan probe, the government said.
Meanwhile, authorities in the eastern city of Nanjing suspended the operations of the city's Xingwang slaughterhouse after pigs there tested positive for clenbuterol.
The banned additive can speed up muscle building and fat burning to produce leaner pork, but causes dizziness, heart palpitations, and profuse sweating if eaten by humans.
Reported by Luisetta Mudie.