A burglar used a rock to gain entry to a Nelson jeweller, taking off with several pieces of jewellery.
Police said an offender entered Jens Hansen Jewellers on Trafalgar Square about 2.35 this morning.
The rock was then used to smash open glass cabinets inside the shop.
Police would like to hear from anyone who was in the central Nelson area at the time of the burglary.
Any information can be provided to be police on 03 546 3840, or anonymously to Crimestoppers on 0800 555 111.