Authorities in Shanghai have pulled the carcases of nearly 3,000 pigs out of the Huangpu river, a major source of drinking water for the city, sparking health concerns.
Some of the pigs were traced from their ear tags to Jiaxing city in neighboring Zhejiang province, and a common porcine virus has also been detected in the the river, which supplies much of Shanghai with drinking water, official media reported on Monday.
The municipal government said it is working with neighboring provinces to trace the origin of the carcasses, Xinhua news agency quoted local officials as saying.
"[They] have warned riverside residents to refrain from dumping animals into the river," it said.
The carcasses were apparently dumped following a disease outbreak that has killed more than 10,000 pigs in recent weeks, the Jiaxing Daily News reported.
"We have been discovering dead pigs on and off in the Huangpu river since January," said a government worker who helped with the clean-up operation. "To begin with, there weren't many of them; just a few at a time."
But there had been a sharp increase in the number of carcasses since last week, he said.
"Now it's out of control; the whole lot is coming this way," the employee said, before hanging up the phone.
An official who answered the phone at the Shanghai environmental protection bureau said the exact source of the carcasses was still unknown.
"They haven't managed to discover where they're coming from yet," the official said. "But I don't know much about it because I didn't go to the scene."
"As soon as they've found out, they will definitely make an announcement," he said.
Tests revealed the presence of the porcine circovirus (PCV) in a recent water sample taken from the river, Xinhua quoted the Shanghai municipal agricultural commission as saying.
"The virus causes porcine circovirus disease in pigs but does not spread to human beings," the statement said.
It said tests for common pig-borne diseases like foot and mouth, swine fever, hog cholera and epidemic diarrhea had so far turned up negative.
Netizen reaction
The incident sparked renewed fears over health and safety among netizens and local residents, as well as biting satire.
"Living in a country like this, my first reaction wasn't anger, but a sense of gratitude," microblog user @phz_vivian wrote.
"I want to thank them for not turning [these pigs] into sausages, or mincemeat, and making dumpling filling out of them, and then selling them to us!"
User @zuogezideqilederen wrote, in reaction to official assurances that water quality in the Huangpu river hadn't been affected: "So could the water testing officials please take a drink of it? I don't believe them."
"I believe them," wrote user @hanbaonaiba, in a reference to the melamine-tainted milk powder scandal. "Doesn't Chinese infant formula have a 99 percent quality control pass rate?"
A Shanghai resident surnamed Yin said he blamed local officials. "They should have a whole range of measures for dealing with an epidemic, not just throwing them in the river," he said.
But he said he wouldn't be giving up pork. "You have to eat pork," he said. "I'll just buy it from the big supermarkets, and rely on my own inspection."
"I'll probably quit eating it from those roadside places, though."
The pig incident is the latest in a string of water pollution scandals to hit China, where one-fifth of waterways are so polluted that they are too toxic for humans to have contact with the water, while at least 40 percent of rivers are seriously polluted, officials say.
Last month, data from Beijing revealed that around 90 percent of groundwater in China is polluted, much of it severely, with activists blaming local governments for protecting polluting enterprises.
In a recent survey of water quality in 118 cities across China, 64 percent of cities had "severely polluted" groundwater, Xinhua news agency quoted experts from the ministry of water resources as saying.
More than three decades of rapid economic growth have sent China’s waterways into a severe environmental crisis, officials say, with a number of high-profile industrial accidents along major rivers in recent years.
Campaigners say that China has a comprehensive set of environmental protection legislation, but that close ties between business and officials mean that it is rarely enforced at a local level.
Reported by Yang Fan for RFA's Mandarin Service. Translated and written in English by Luisetta Mudie.