Chinese officials have fished 2,200 dead pigs out of Shanghai's Huangpu River, which is used as a drinking water source for many residents.
According to a statement posted on Shanghai's Agriculture Committee's website there is no evidence the pigs were dumped in the river, nor of any animal epidemics.
The city's water supplies bureau had insisted the water quality has not been affected, China Daily reported.
But fears of water pollution were emerging on Monday after the number of carcasses climbed from 900 to 2,200, Reuters reports.
The Global Times quotes Xu Rong, director of Shanghai Songjiang District Environmental Protection Bureau as saying: "We have to act quickly to remove them all for fear of causing water pollution."