Yu Kangzhen, China's chief veterinarian with the Chinese Ministry of Agriculture(MOA), also said water in the Huangpu River, where a great number of dead pigs were found, meets national standards for drinking water.

Dr Kangzhen, who heads an MOA inspection team here, said the number of floating dead pigs have declined greatly, and the bodies have been retrieved in a timely manner and handled properly.

Dr Kangzhen urged local authorities to continue to fish pig carcasses, and make sure there are no further dumping dead pigs in rivers. He also vowed to keep any dead pigs away from the market.

More than 6,000 pig corpses have been retrieved from the Huangpu River over the last few days, and the river provides 22 percent of Shanghai's tap water.

Zhejiang province's city of Jiaxing, which is located on the river's upper reaches, is believed to be the source of the dead animals.

Dr Kangzhen said sample examinations of dead pigs have confirmed that there were no swine epidemics in Jiaxing, and he attributed the pig deaths to common diseases due to bad weather in the city.

The senior vet said it is natural to see dead pigs as there are a great number of small hoggeries in Jiaxing. When pigs die of diseases, local hog farmers often dump the carcasses into the river or on rural roads.

Dr Kangzhen said the team has asked local authorities to step up hygiene education among hog farmers and production supervision on pig breeding.