Around 1,000 duck carcasses appeared on the Nan River in Pengshan County, Sichuan, last week.
The cause of the ducks' death is unknown, and many of the bodies had begun to rot by the time they were discovered, so there was no way to find out with certainty the cause of death.
Most were wrapped in bags, indicating that they had been dumped into the river.
However, their rotting state indicated that they had already been dead for several days, making it unlikely that any local farmers were guilty of the illegal dumping. Additionally, no duck farms are located within a kilometer of where the duck bodies were found. The area is sparsely populated.
Authorities suspect that the duck bodies came from much farther up river.
Officials disinfected the bodies and buried them in a pit.
The incident will not affect the water supply, officials said. The case is still under investigation.
The news follows a report last week that around 16,000 pig carcasses were found in a river in Shanghai.