South China Morning Post reported Monday that Chinese officials have pulled at least 3,323 swollen and rotten dead pigs from a Shanghai river since Thursday including one that tested positive for the swine virus.
The dead pigs were found floating at the Songjiang district section of the Huangpu River that flows through Shanghai, which is a drinking water source for city residents.
The city government, citing monitoring authorities, said the drinking water quality has not been affected, despite the positive test of the swine virus, Pocine Circovirus type 2 or PCV-2. Officials say the virus is not known to cause disease in humans.
Shanghai's Agriculture Committee said authorities don't know yet what caused the pigs to die or why they were dumped in the river. However, the dumping follows a crackdown on the illegal trade in contaminated pork.
In China, pigs that have died from disease should be either incinerated or buried, but some unscrupulous farmers and animal control officials have sold problematic carcasses to slaughterhouses.
The pork harvested from such carcasses has ended up in markets. As a food safety problem, it has drawn attention from China's Ministry of Public Security, which has made it a priority to crack down on gangs that purchase dead or sick pigs and process them for illegal profits.
"According to the law, dead pigs must be burned or buried, but if there is not enough regulatory monitoring, it's possible some of them will be sold into the market at low prices," Zheng Fengtian, a professor at the School of Agricultural Economics and Rural Development at Renmin University in Beijing.
Zhejiang police said on their official website that police have been campaigning to crack down on pork meat harvested from sick pigs and that the efforts were stepped up this winter as Chinese families gathered to celebrate the Lunar New Year in February.
Shanghai's city government said initial investigations have found the dead pigs had come from the upper tributaries of the river in Jiaxing city in Zhejiang province.
Jiaxing local media reported last week that more than 18,000 pigs from one village have died from illness in the last two months. The reports have sparked fears that residents dumped all of the diseased animals in the river.
CCTV reported local residents near Huangpu River saying that dumping dead, diseased pigs in the river was common practice.