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.

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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.