More than 900 dead pigs were picked up from Shanghai's Huangpu River as of March 9 afternoon, local authorities said.
The dead pigs were spotted in the Songjiang section, the upstream of the Huangpu River and a drinking water source for Shanghai residents, according to the city's water supplies bureau.
"The dead pigs can be seen every day and every year, and the number is much greater than those in previous years," said a resident.
Shanghai Songjiang Environmental Protection Bureau said they have carried out daily patrol on river to pick up any bodies they find.
"We pick up the dead pigs from morning to night. We cannot do it at night for safety concerns, so we usually begin at 06:30 to the dark," said Xu Rong, director of Songjiang Environmental Protection Department.
Xu said the dead pigs do not wear the ear tags of Songjiang.
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The bureau said the water quality has not been affected. However, to ensure tap water safety, local environmental protection and water supply authorities have beefed up quality examination at the water intakes as well as the whole water disinfection process.
The Shanghai Agriculture Committee have carried out bio-safety treatment on the dead pigs. It is investigating where the dead pigs may have come from.
The committee said so far it has not received reports of animal epidemic outbreaks in the city.