Ye's father chimed in.

"Here people would be fined if they threw pigs into rivers," he said, as a light rain fell over the lush, green barley fields that surround the village of mostly ochre-colored, two-story homes. "There are government people collecting dead pigs."

But earlier this week, a Zhulin village official, Wang Xianjun, told a local newspaper that 18,000 pigs had died here in January and February. A Zhejiang official attributed a spate of pig deaths in the province to cold weather. Also this week, the Shanghai municipal government said nearly 6,000 dead pigs had been pulled from the Huangpu River.

When NPR called a village office asking for Wang — the Zhulin official – workers there said he didn't exist. When I traveled two hours from Shanghai to Zhulin and actually went to the local government office, workers there said Wang was away at a meeting and they declined to supply his cellphone number.

Hong Kong's South China Morning Post quoted Zhejiang villagers saying farmers dumped pigs in the river because there were too many for government disposal areas. In addition, villagers said some farmers may have dumped pigs because of a crackdown on selling diseased pigs for human consumption.

Pork is the most popular meat in China. Half the world's pigs live there, as The Salt has previously reported. China's state media reported this week that 46 people have been jailed in Zhejiang for selling diseased pigs. Last year, police in the province confiscated about 11 tons of meat from sick pigs, according to the state-run China Daily.

Back downstream in Shanghai, a hyper-modern metropolis of 23 million, some people are confused and incredulous.

"We really hope an inspection body or government can come out to tell us how exactly these pigs died," said a woman named Wang, 27, who works in the media business here. "You can't just say the pigs died of cold weather. That's a pretty laughable statement."

Shanghai officials say one water sample from the river contained porcine circovirus, which cannot be passed on to humans. Government officials also insist the drinking water supply, which draws in part from the river, remains safe.

Wang is dubious.

"People in Shanghai think it's better not to eat pork, because they worry diseased pigs would end up on their dinner tables," says Wang. "People say the water we use to brush our teeth is pork broth."

Frank Langfitt is NPR's Shanghai correspondent.

Copyright 2013 NPR.

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Shanghai's Dead Pigs: Search For Answers Turns Up Denials