Rail services have been suspended between Dalkey and Greystones due to a fire that damaged signalling equipment.
The fire occurred at a signalling equipment room in Bray at around 11.30pm last night.
Iarnród Éireann has said services will not resume until Monday morning.
It is believed to have been caused in the relay room and not as a result of vandalism or criminal damage.
DART services are operating between Dalkey and Howth/Malahide.
Passengers looking to Killiney, Shankhill, Bray or Greystones are advised to transfer to Dublin Bus services at Dún Laoghaire.
Dublin Bus will accept rail tickets during the suspension.
Rail services from Connolly Station to Rosslare Europort will have bus transfers between Connolly and Greystones.