Vandals on the Wadden island of Texel have damaged two ancient boulders by painting symbols and throwing paint over them.

The boulders, which are thought to be some 500 million years old, were found in the ground in the Waalenburg nature reserve and weigh 7 tonnes and 4.5 tonnes respectively.

The Texel local authorities decided to raise the boulders and put them on show beside a cycle path and last Friday removed the work fences to make them accessible to the public. The incident took place the next day.

In natuurgebied #Waalenburg op #Texel zijn meerdere potten verf geleegd over 500 miljoen jaar oude zwerfkeien. Het is nog onduidelijk wanneer en hoe de verf wordt verwijderd. De provincie overlegt hierover met Natuurmonumenten. https://t.co/357EKsoMem pic.twitter.com/QoE2vw53ce

— Noord-Holland (@ProvincieNH) April 23, 2019

‘It is very annoying,’ a spokesman for Noord-Holland province said. ‘We don’t know what type of paint it is and how easy it will be to clean it off.’

Heritage body Natuurmonumenten and the province have reported the incident to the police and are calling on anyone with information to come forward.