Some 900 dead pigs had been retrieved from Shanghai's Huangpu River as of yesterday afternoon, local authorities said.

Pig carcasses were first spotted on Tuesday in the upstream Songjiang section of the Huangpu River.

This is a tap water source for some Shanghai residents.

The bureau said that water quality has not been affected.

However, to ensure tap water safety, local environmental protection and water supplies authorities say they have beefed up quality examination at water intakes as well as the disinfection process.

The Shanghai Agriculture Committee has carried out bio-safety treatment on the retrieved dead pigs.

It is currently investigating where the animals may have come from.

Earlier reports said they may be from a farm on the upper tributaries in Zhejiang Province.

The committee said it has not received any reports of animal epidemic outbreaks in the city.

Local authorities are still retrieving dead pigs to avoid water contamination.