Over 2,800 pigs have been found dead in one of Shanghai's main water sources triggering a public outcry in China where concerns over food safety run high.
The carcasses were probably dumped in the Huangpu river in Zhejiang province and the total number was expected to increase, Xu Rong, director of Shanghai Songjiang District Environmental Protection Bureau, said.
"We have to act quickly to remove them all for fear of causing water pollution," she was quoted as saying as the national parliament, where pollution has been a hot topic, met in Beijing.
Officials were investigating, media said.
An official at the Songjiang environment bureau declined to comment when contacted by Reuters.
The Shanghai government said in a statement posted on its website that workers were continuing to collect carcasses from the river and it was closely monitoring the water quality although no pollution has been found so far.
Water contamination, caused by fertiliser run-off, chemical spills and untreated sewage, is a major concern in China.
The Chinese government is planning to invest $850 billion over the next decade to improve the water supply system.
The discovery of the dead pigs over the weekend quickly made the rounds in social media, with many bloggers criticizing the authorities for their delayed response.
"Related government departments should seriously investigate this and get to the bottom of it," said one blogger by the name of Ting Tao.
"The government should really pay attention to people's lives and take no time to solve food safety issues."