Police are investigating a reported unauthorised excavation at an Iron Age site in the Western Isles.
Dun Torcuill, a small uninhabited island in North Uist, has the archaeological remains of an ancient stone-built tower called a broch.
Stones have been cleared away, damaging the legally protected scheduled monument.
Police Scotland said it received a report of the damage on 22 October and was now appealing for information.
Officers have been working with Historic Environment Scotland on the investigation.
Sgt Gavin McDevitt, of Lochmaddy Police Station, said: "Damaging or removing any part of a scheduled monument is a criminal offence.
"In this instance, there is the potential for destabilisation of the monument, and the loss of archaeological deposits previously protected by the tumbled stone."
He added: "It is an offence under the Ancient Monuments and Archaeological Areas Act 1979 to undertake works without Scheduled Monument Consent.
"The penalties for offences under the Act are considerably higher than those for damage to property or vandalism offences, with fines ranging up to £50,000 or prison sentences of up to two years."
Historic Environment Scotland said it would urge anyone with information on the incident to contact police.
Brochs are some of Scotland's oldest and most formidable structures to be found in Scotland, many of them in the Highlands, the Western Isles and Orkney.