The bodies of 25 ponies with no obvious wounds have been dumped near a cliff in northern NSW, police say.

A tip-off on Saturday afternoon led police to a truck parking bay three kilometres south of Old Ben Lomond Road near Glen Innes.

The officers followed tracks to a nearby cliff, where they spotted the bodies of 25 ponies of various colours and ages in the early stages of decomposition.

There were no obvious wounds on the animals or any other indication as to the cause of their death, police said.

There were no brands, tags or any identifying marks that could help police find their owner.

"We're keeping a very open mind because we have very little to go on," Inspector Rod Shoesmith, of Armidale police station, said.

"They were found dumped over the side of a parking bay, down a steep cliff.

"I've never seen anything of this magnitude. It was a disturbing scene."

Officers photographed the animals then buried their remains at the site. They believe a small- to medium-sized truck was used to dump the ponies.

Gary Tarrant, who lives on Old Ben Lomond Road, was baffled by the crime.

"No one around here would have 25 horses," he said. "We've got a couple. Most people have a couple."

Anyone who noticed suspicious or unusual behaviour in the area is urged to contact Glen Innes Police or Crime Stoppers on 1800 333 000.