At least 35 tonnes of dead fish have washed up in a lake in southern China.

The fish were found floating on the surface of Hongcheng Lake. Dozens of sanitation works have been put to work cleaning up the fish in an effort to prevent any of them being sold to consumers.

Reports in the Global Times say the government is still investigating the cause of the phenomenon, though experts have speculated that the death of the fish was a result of fluctuations in the waters saline levels.

Experts said the fish likely came from the larger, saltier Nandu River, before experiencing a sudden drop in salinity levels when the tide swept them into the freshwater Hongcheng Lake.

Saltwater fish cannot survive in fresh water, as more water is able to enter their bodies causing blood vessels to rupture.

Despite expert statements, reports say that the public are still concerned that the deaths may have been caused by pollution, which may also harm the human population.