Chinese officials say they have fished out 900 dead pigs from a Shanghai river that is a water source for city residents.

Officials are investigating where the pigs came from. A statement posted Saturday on the city's Agriculture Committee's website says they haven't found any evidence that the pigs were dumped into the river or of any animal epidemic.

The statement says the city and Songjiang district governments started retrieving the pigs on Friday night. By late Saturday afternoon they had recovered and disposed of more than 900.

The statement says the water and environmental protection bureaus are ramping up monitoring of the river's water quality.