Chinese workers have fished more than 12,000 dead pigs out of a main waterway in the cities of Shanghai and Jiaxing over the week, in a scandal that has spotlighted China's troubles with food safety, according to officials.
The South China Morning Post newspaper quoted government sources as saying on Sunday that nearly 9,000 swine carcasses were found in a river in Shanghai, and 3,600 others in Jiaxing, with the search continuing in both cities.
Authorities have also found traces of a common pig virus in some of the animals floating in the Huangpu River this week.
"Shanghai's animal control authority found porcine circovirus, a common disease among hogs that was not known to infect humans, in 13 of 20 samples of internal organs taken from dead pigs retrieved from the Huangpu," the newspaper quoted Ministry of Agricultural as saying.
The swine effluent discovered flowing down the Huangpu river - which supplies a fifth of the commercial hub's drinking water - has added the country's most popular meat to a growing list of food items rocked by scandal.
Authorities also said that after intensified checks they have not found any substandard pork products on the market and were closely monitoring water quality.
Shanghai has blamed farmers in neighbouring Zhejiang province for casting pigs thought to have died of disease into the river upstream, although officials from the area have admitted to only a single producer doing so.
Pork accounted for 64 percent of total meat output last year, and China's increasingly wealthy urban residents consumed 21 kilograms (45 pounds) of the meat per person in 2011.
Despite laws against the practice, animals that die from disease in China can end up in the food supply chain or improperly disposed of.
China faced one of its biggest food-safety scandals in 2008 when the industrial chemical melamine was found to have been illegally added to dairy products, killing at least six babies and making 300,000 people ill. Levy
Cheap recycled cooking oil is available nationwide, made illegally from leftovers scooped out of restaurant drains. Amid public disgust, authorities arrested more than 30 people over its sale, but the practise continues.
In another recent incident, the American fast-food giant KFC faced controversy after revealing that some Chinese suppliers provided chicken with high levels of antibiotics, in what appeared to be an industry-wide practice.