Chinese police are investigating the poisoning of more than 200 swans at a lake in Inner Mongolia.
Police said traces of pesticide were found in the swans' bodies, and that they were likely killed by poachers.
The mass deaths were discovered last week at Hongtu Lake, which is famous for hosting migratory swans.
The authorities are offering 100,000 yuan (£12,080; $14,760) for information leading to the suspects' arrest, state media report.
Besides the 233 tundra swans, another 26 mallards were also found dead at the lake, whose name in Mongolian means "Swan Lake", according to local reports.
State broadcaster CCTV reported that the discovery was first made by an elderly couple who went to the lake on 19 October to take pictures of the swans, only to see scores of dead birds floating on the surface.
Traces of carbofuran, a type of pesticide commonly used by poachers, were found in the swans' bodies.
Tian Yangyang, from environmental organisation Let Birds Fly, told the Sixth Tone website that many poached swans end up in restaurants in China, some of which offer "swan feasts" on their menus.
Despite the fact that many poached animals are killed with poison, "most people believe eating wild animals is healthy," he said.