The number of dead pigs found floating from a major river near China's financial hub, Shanghai, has risen to nearly 6,000, state media has reported.

Workers scoured the banks of the Huangpu River in boats on Tuesday for more carcasses, broadcaster CCTV showed.

The state-run Xinhua news agency quoted Shanghai authorities as saying that the number of swine carcasses found had risen to over 5,916 since the first batch were fished out last Friday.

Tags collected from the ears of the pigs suggested that they had come from Jiaxing City in Zhejiang Province upstream, Xinhua reported.

Xinhua quoted sources at Shanghai's municipal agricultural commission as saying that one water sample from the river found porcine circovirus, a virus that affects pigs but cannot spread between people, but that all other tests showed no signs of abnormal contaminants or disease.