Thirteen mountain bikes have been stolen in the Kilbroney Park area of Rostrevor.
The incident happened sometime overnight between Friday and Saturday.
Only around three weeks ago, a string of obstacles – including logs and tightly-pulled pieces of cord – had been placed along an off-road trail at the park which is used by mountain bikers.
The PSNI have advised anyone who is offered a mountain bike for sale to be wary about where it might have come from.
Anyone with information is asked to contact police at Ardmore on the non-emergency number 101, quoting reference number 402 23/07/16, or call the independent charity Crimestoppers and speak to them anonymously on 0800 555 111.