Authorities in Shanghai and east China's Zhejiang Province reassured the public on Friday that no swine epidemic has been detected after more dead pigs were fished out of local rivers.
The municipal government of Jiaxing said another 3,601 dead pigs have been retrieved from rivers and roadsides around the city.
The corpses of nearly 6,000 pigs were pulled out of the Huangpu River from March 8 to 13. The river provides 22 percent of Shanghai's tap water.
Jiaxing, which is located on the river's upper reaches, is suspected of being the source of the dead animals, as ear tags on the corpses indicate where they were born.
A government spokesman said Friday that the city has sent personnel and ships to remove the carcasses from the river, as well as inspect local pig farms.
The spokesman said cold winter weather caused the survival rate for piglets to decline.
The pigs were dumped over a period of more than two weeks, the spokesman said.
The Shanghai government said 809 pig carcasses were retrieved on Friday.
The municipal water affairs department said tests indicate that the city's water quality is safe and meets national standards for drinking water.