Health and public security officials in Heyuan city, Guangdong, have detained six people after contaminated pork triggered a massive food poisoning outbreak last week.
Those being held include three pig farmers, a fodder shop manager and two sales managers, the People's Daily Web site reported yesterday.
Police put the pig farmers under investigation after they allegedly sold the pork that triggered last Wednesday's outbreak, which affected almost 500 people.
The pigs were apparently treated with clenbuterol, an asthma drug that makes pork lean, the report said.
Police also placed a fodder shop manager, surnamed Chen, under investigation.
Chen is believed to have supplied the farmers with clenbuterol-tainted fodder.
Seven 20kg bags of the fodder were seized from Chen's shop.
Two sales managers from a fodder supply company in Guangzhou were also placed under investigation.
More than 480 people were admitted to hospitals following Wednesday's outbreak.
Most have been discharged but some are still receiving treatment.
Quoting a spokesman from the official consumer rights group, Xinhua reported on Thursday that food safety was a major concern among customers.
Statistics from the 1998-2000 period showed that food-related consumer complaints accounted for 20 per cent of all gripes, the secretary-general of the Chinese Association of Consumers, Ning Wanglu, said.
On average, food purchases accounted for about 40 per cent of all consumer sales in China, the association said.