Mystery surrounds the death and mutilation of swans in a park.
A runner called the police after spotting dead birds and another that had had its wing chopped off.
Police have also received reports that a swan had been plucked.
Wildlife crime officers from Derbyshire Police are looking into the incidents which happened at the gravel pits on Meadow Lane, Long Eaton.
A spokesman for the force said: “Our investigations at this stage lead us to believe that the birds were not killed by an animal such as a fox and we are looking at what motive there may have been for someone to have done this as a deliberate act of cruelty.
“We are appealing for anyone with any information or anyone who may have witnessed suspicious behaviour in the area to get in touch with us.”
Call police on 101 or speak anonymously to Crimestoppers on 0800 555111.