SHANGHAI, Mar. 11 (Xinhua) -- The number of dead pigs found in Shanghai's Huangpu River increased to 2,800 after an extra 1,600 of the corpses were fished out by Sunday evening, city authorities announced on Monday, adding that they may have come from neighboring Zhejiang Province.
Labels pinned in the ears of the pigs for tracing purposes have indicated they come from the upper reaches of Jiaxing City in east China's Zhejiang Province.
Local media in the Jiaxing region have reported residents dumping dead pigs into the river since March 4, authorities with the Information Office of Shanghai Municipality said.
Jiaxing authorities admitted the dumping of dead pigs in the water, but pointed out the labels on the ears only indicate the birthplace of the animals, while where they spent the rest of their lives is still unknown.
Laboratory tests found porcine circovirus in one water sample taken from the Huangpu River, a water source for city residents, according to sources with the Shanghai municipal agricultural commission.
The virus can spread among pigs but not to human beings, a commission statement said.
All other tests on the river water provided negative results.
Water quality in Shanghai has not been affected by the floating pig cadavers, according to the city's water supply bureau. Water quality in the Huangpu River is similar with last year, it said.