With the recovery of 611 more pig carcasses, the number of dead pigs found in a Shanghai river Saturday reached nearly 9,000.
The Shanghai authorities, however, are assuring the residents that tap water is safe.
The dead pigs, being recovered since March 8 from Huangpu river, are largely believed to be from the upstream city of Jiaxing in neighbouring Zhejiang province, the Shanghai Daily reported on Sunday.
However, the chief vet for Chinese Agriculture Ministry Yu Kangzhen, investigating the deaths, said there had been no major swine epidemic. But he said some samples tested positive for common porcine circovirus, a small DNA virus that infects pigs, and a diarrhoea virus.
Yu said no dead pigs in Jiaxing were found to have entered the market.
The vet said cold weather and fluctuating temperatures have caused a spike in deaths among piglets. When pigs die of disease, local hog farmers often dump the carcasses into rivers or on rural roads.