Pig carcasses — about 14,000 of them — have been floating down rivers that feed into Shanghai for nearly two weeks. The city’s residents have been told not to worry, and not much else.

Where the pigs came from, how they died and why they suddenly showed up in the river system that supplies drinking water to a city of 23 million has not been explained. Officials have told residents that their drinking water is safe and have censored microblog posts suggesting that the public organize peaceful protests.

The official response reminds many of the government’s reticence about previous health concerns, including the SARS and bird flu bird epidemics and the scandal over chemically adulterated milk and infant formula.

“They are only giving the runaround,” said Huang Beibei, a Shanghai microblogger whose shocking photographs of the pigs prompted local media coverage and government attention. “’Who believes what they are saying?”

“Those pigs must have come from somewhere,” author Li Mingsheng said. “That’s a basic question, but the government still has not told us that.”

Authorities had retrieved at least 13,996 dead pigs as of Wednesday, and they have released daily bulletins saying that drinking water in Shanghai continues to meet national standards.

Official comment has been essentially limited to pig tallies by Shanghai authorities and one late-night news conference by a local official in nearby Zhejiang province, where the pigs are suspected to originate. Otherwise, no top official and no head of any government agency dealing with the environment, health or agriculture has made any public comment.

Officials have punished only eight small-time hog farmers whose pigs could be traced through ear marks. The farmers, in the Zhejiang town of Jiaxing, where hog farming is a major industry, each received a fine of less than 3,000 yuan (about $480).

The central government in Beijing, which has been enmeshed in a leadership transition, dispatched a chief Agriculture Ministry veterinarian, but Yu Kangzhen’s conclusion was merely that there had been no major outbreak of swine disease to explain the dumping.

Villagers have told local media that pig dumping surged after a police crackdown on the illicit trade in pork products harvested by butchering dead and diseased pigs. With no black-market traders to collect the dead pigs, farmers are dumping them in rivers, they say. Other observers have suggested that farmers are feeding pigs small amounts of arsenic to make their skins look shinier, thus increasing the mortality rate. Government officials have not addressed either theory.

— Associated Press