BEIJING -- A surge in the dumping of dead pigs upstream from Shanghai -- with more than 2,800 carcasses floating into the financial hub through Monday -- has followed a police campaign to curb the illicit trade in sick pig parts.

The effort to keep infected pork off dinner tables may be fueling new health fears, as Shanghai residents and local media fret over the possibility of contamination to the city's water supply, though authorities say no contamination has been detected.

Authorities have been pulling out the swollen and rotting pigs, some with their internal organs visible, since Friday -- and revolting images of the carcasses in news reports and online blogs have raised public ire against local officials.

"Well, since there supposedly is no problem in drinking this water, please forward this message, if you agree, to ask Shanghai's party secretary, mayor and water authority leaders if they will be the first ones to drink this meat soup?" lawyer Gan Yuanchun said on his verified microblog.

On Monday, Shanghai officials said the number of dumped adult and piglet carcasses retrieved had reached 2,813. The city government, citing monitoring authorities, said the drinking water quality has not been affected.

Shanghai's Agriculture Committee said authorities don't know what caused the pigs to die, but that they have detected a sometimes-fatal pig disease in at least one of the carcasses. The disease is associated with the porcine circovirus, which is widespread in pigs but doesn't affect humans or other livestock.

Shanghai's city government said initial investigations had found the dead pigs had come from Jiaxing city in neighboring Zhejiang province. It said it had not found any major epidemic.

Huang Beibei, a lifetime resident of Shanghai, was the first to expose the problem when he took photos of the carcasses and uploaded them onto his microblog on Thursday.

"This is the water we are drinking," Huang wrote. "What is the government doing to address this?"

His graphic photos apparently caught the attention of local reporters, who followed up.

Huang said he's most concerned about water safety. "Though the government says the water is safe, at least I do not believe it -- given the number of the pigs in the river. These pigs have died from disease," Huang said.

The dumping follows a clampdown on the illegal trade in contaminated pork.

In China, pigs that have died from disease should be either incinerated or buried, but some unscrupulous farmers and animal control officials have sold problematic carcasses to slaughterhouses. The pork harvested from such carcasses has ended up in markets. As a food safety problem, it has drawn attention from China's Ministry of Public Security, which has made it a priority to crack down on gangs that purchase dead diseased pigs and process them for illegal profits.

Zhejiang police said on their official website that police have been campaigning to rid the market of unsafe pork meat and that the efforts were stepped up this winter as Chinese families gathered to celebrate the Lunar New Year in February.

In one operation last year, police in Jiaxing broke up a criminal gang that acquired and slaughtered diseased pigs. The provincial authorities said police arrested 12 suspects and confiscated nearly 12 tons of tainted pork meat.

"Ever since the police have stepped up efforts to crack down on the illicit market of sick pigs since last year, no one has come here to buy dead pigs, and the problem of pig dumping is worse than ever this year," an unnamed villager told the Jiaxing Daily newspaper, which is run by the local Communist Party.

Wang Xianjun, a government worker for Zhulin village, told the newspaper that villagers were breeding too many pigs.

Wang said the village had 10,078 dead pigs in January and another 8,325 in February. "We have limited land in the village," he said. "We do not have that much land for burial."

Zheng Fengtian, a professor at the School of Agricultural Economics and Rural Development at Renmin University in Beijing, acknowledged that there is illegal trade in diseased dead pigs in China.

"According to the law, dead pigs must be burned or buried, but if there is not enough regulatory monitoring, it's possible some of them will be sold into the market at low prices," he said, adding that it isn't known how serious the problem is.