Police in Glenn Innes have found 25 dead ponies dumped near a cliff in northern NSW and is asking the public for information about a truck that may have been used to bring the animals there.

The decomposing ponies of mixed ages and colors were found on Saturday 3 kilometres south of Old Ben Lomond Road, near a truck parking bay, after a tipoff by a concerned citizen. Investigators found no signs in the animals indicating the cause of death.

New England Local Area Command duty officer Rod Shoesmith also said there was no sign that the Hendra virus killed the ponies.

"We have no information, evidence or any indication that the cause of death may be related in any way to Hendra," said Shoesmith, according to Northern Daily Leader.

The hendra virus is a rare, emerging virus transmitted to humans from animals that can cause respiratory and neurological disease and death in people. It can also cause severe disease and death in horses, resulting in considerable economic losses for horse breeders.

The police took photos of the carcasses and buried them at the same location.

New England Local Area Command acting duty officer Stuart Gray believes a huge truck was used to dump the dead horses and appealed to anyone who have seen or heard something in the area to come forward or contact the police.