DNA testing will be carried out on a skull, which could possibly that of racing legend Shergar who was kidnapped in 1983.
The decayed head was discovered in Tralee, Co Kerry, last Saturday by Councillor Tommy Foley, during an annual clean-up of a glen outside the southwest Ireland town.
Thursday it was taken by Gardai to Naas police station in Co Kildare, where the theft was first investigated 17 years ago.
'DNA testing will be done to establish if it is the head of Shergar,' said a police spokeswoman.
Mr Foley said the remains were hidden in a sack at the bottom of a ditch.
'There were two bullet holes in the head and it was definitely a racehorse's head. I was there with a farmer's son and he said it was not an ordinary horse.
'It's just three miles from Tralee and it would be a place where you would conceal the remains unseen for years.
'There is a possibility that it was him because when Shergar was abducted there was a Kerry connection.'
When Shergar was retired in September 1981 he had won six races, including both the British and the Irish Derbys, and collected 436,000 pounds in prize money.
But two years later the horse was kidnapped by an IRA gang from the Ballymany Stud in Co Kildare, where he had embarked upon his new career as one of the most valuable stallions in the world.
Negotiations with the kidnappers continued for four days and a Polaroid photograph was provided showing Shergar with an up-to-date copy of the Irish Times before the kidnappers suddenly fell silent.
The kidnapping became one of the great mysteries of the 1980s, with constant reports of sightings, but despite a nationwide search no trace of him was ever found.
Insurers refused to pay out without proof of the horse's death.
Former IRA man Sean O'Callaghan, who is from Co Kerry, later claimed that the horse had been killed by his abductors who were unable to handle him.
O'Callaghan, a convicted murderer who turned police informer, said the paramilitary group had demanded a 5 million pound ransom.
Des Leadon, the head of clinical pathology at the Irish Equine Centre who has investigated a number of horse corpses believed to have been Shergar, said that DNA testing would have to be used to determine if the finding is the real Derby winner.
'There have been so many sightings over so many years that it is difficult to prejudge them,' he said.
'One horse looks very much like another to an untrained eye, and it is only through detailed testing that we can check.
'First we need to make certain that it is equine, then determine the age and other factors, and then, if these things point to it being a racehorse, we would use DNA testing.'
Leadon said the decay to the corpse would make identification difficult but was confident that it could be done through scientific methods.
'We are very keen to find the real Shergar because if we can show it is possible to identity him after all this time it might deter other people from kidnapping horses for ransom,' he added.
