Officers are trying to establish who the man is, and where and how he died.
Det Ch Insp Phil Poole, from the Major Crime Unit, said: “We are keeping an open mind, but we believe that this man has been hit by a vehicle, and then has been moved to the park.
“I urgently want to hear from anyone who believes they may have hit someone in their car yesterday, or who has noticed a change in behaviour from someone they know who drives, or who has noticed damage to a vehicle.
“It’s vital that we trace that person as quickly as possible so that we can get their account of what happened.
“If anyone in the area has found that their wheelie bin with a green lid has been stolen, I also want to hear from them.”
Anyone with information, or who has dashcam or CCTV footage from the area, has been asked to get in touch.
Officers remain at the scene on Saturday carrying out inquiries.