Thousands of fish have washed up dead in a lake in eastern China due to water pollution.

The shocking video, filmed in Suqian City in Jiangsu Province on Tuesday (August 28), shows a man using a fishing net to catch the dead marine life, including fish and crab, on the surface of Hongze Lake and placing them into his boat.

Black, foul-smelling water entering the lake from upstream polluted the lake and was responsible for killing the marine life and causing severe losses to fish farmers, according to local reports.

The precise source of the pollution was still unknown and an investigation was underway, reports said.