Dart services have been temporarily suspended between Bray and Dalkey because of a fire adjacent to the line north of Killiney, in south Dublin.
Overhead lines had to be de-energised to allow firemen cross the track to fight the fire.
Dublin Bus is accepting rail tickets.
A spokeswoman for Iarnród Éireann said she did not know when services would resume.
It is not known what caused the fire which started about 6.15 pm.
