Vandals have made three separate attacks on the railway line between Corwen and Llangollen during the past week.
In a message to its members in the area, the local Neighbourhood Watch team says the first incident happened between last Friday and Saturday when objects were thrown through the windows of a signalbox at the Glyndyfrdwy level crossing.
Then, sometime between Sunday and Monday, the vandals returned to smash another window in the box by throwing an object through it.
Third incident was at the same location when a railway wagon was broken into with windows being smashed and graffiti daubed on to the walls.
* If you noticed anything suspicious, or have any information relating to this incident please contact North Wales Police by dialling 101.
Alternatively, you can provide information anonymously by calling Crimestoppers Wales on 0800 555 111. North Wales Police would like to urge residents to always report suspicious activity to them at the earliest opportunity.