Horse limbs were found dumped in rubbish bags in a playing field in Watford.
The grim discovery at Callowland Recreation Ground on October 8 has been described as a "disgusting behaviour".
Watford Borough Council was alerted to two rubbish bags dumped at the open space in Gammons Lane.
When officers inspected the bags, they found legs from various horses or ponies, a recently shod horses foot, horse shoes and an empty bag of Speedi-Beet.
Speaking on behalf of the council, Amy Bedrock said: "This was a really terrible find and it was disgusting behaviour to have left these in a park.
“The bags were removed immediately.
"We hope that anyone with any information will contact the police and help with the investigation.”
Officers from Hertfordshire Constabulary confirmed they are investigating the incident.
Police are asking anyone with information about where the horse body parts may have come from or who saw the bags being left at the recreation ground to contact them.