(CNN)At least 35 tons of dead fish appeared in a lake in southern China, leaving residents stunned.
The piles of fish washed up in a lake in Hainan province on Wednesday, Chinese state media reported.
Residents expressed concerns on pollution, but local authorities said the fish died as a result of salinity change.
The change in salinity levels likely occurred after a tide pushed the fish up farther into Hongcheng Lake in the city of Haikou, state-run People's Daily reported.
Regional environment officials are still investigating.
It's unclear what kind of fish it was, according to People's Daily. It described it as the size of a half palm, saying residents had not seen that type of fish at the lake before.
Dozens of sanitation employees worked for hours to trash the fish, to prevent it from being sold to consumers.