It is believed the deer were killed and gutted on Saturday night (7 October) in a field by the B4202 near Kidderminster, Worcestershire. However, the deer had been treated with Immobilion, a drug often used on deer that are pets, which can be fatal to humans and harmful to pets.
The police believe the deer were slaughtered for their meat and are urging people not to buy venison from any unrecognised sources.
A spokesman for West Mercia Police said: "Meat from such animals is not intended for human consumption and may also adversely affect domestic pets and animals. The carcases should not be allowed to enter any food chain."