The remains of a horse were discovered in the debris of a fire involving burning rubbish in a field in Thetford last weekend.
A fire crew from the town was called to the A11 at Thetford shortly before 7pm on Saturday after a large amount of smoke was seen near the Mundford roundabout.
Firefighters used hose reel jets to extinguish the blaze which is believed to have been started deliberately and involved burning rubbish in the open.
The remains of a horse were discovered among the debris, but police and fire officials believe the animal died before the fire was started.
Norfolk Police were called to the scene at 7.40pm.
A police spokesman said: “Once extinguished, the remains of a small horse were found in the debris.
“At this time nobody has claimed being the owner of the animal and it is believed the horse had been deceased for some time prior to the fire being set.
“In the absence of a complainant and an unknown motive no further police action can be taken at this stage.”