Shanghai authorities have announced the discovery of traces of porcine circovirus, a common disease among pigs which may be responsible for the over 2,000 animal corpses found in the Huangpu river. The virus is not known to be infectious to humans.

Porcine circovirus, a common disease among hogs that isn’t known to be infectious to humans, was found in a sample taken from the Songjiang section of the Huangpu river, Shanghai’s agriculture department said, citing the city’s animal disease control authorities. Tests conducted hourly on the river, which provides drinking water for some of the municipality’s 23 million residents, were negative for other diseases including foot-and-mouth, swine fever, hog cholera and blue-ear, it said.

The China News Service reported today the total number of carcasses has risen to 2,813, up from the more than 1,200 reported by the government earlier today. A preliminary investigation showed the dead pigs, which include piglets and mature hogs, had floated down the river from neighboring Zhejiang province, the Shanghai government said on its website.

“We have heard increased reports of outbreaks from our customers, and so far they don’t appear to be serious, although they can potentially develop,” James Feng, general manager of Soozhu.com, China’s biggest independent hog researcher, said by phone from Beijing. “Given the magnitude of China’s hog herds, it’s not uncommon to have thousands of pigs killed by diseases,” he said.