Rail services have now resumed between Raheny and Howth / Malahide after a suspect bomb was found earlier on the line north of Kilbarrack in Dublin.
Irish Rail says Drogheda Commuter services and Belfast Enterprise services have also resumed but there are some delays as a result.
Barry Kenny from Irish Rail said that the matter is being dealt with by Gardaí and the Defence Forces.
"A member of our line inspection team was walking the route just north of Kilbarrack station, he had concern about an object that he saw, so he alerted our control and we reported it to the Gardaí," said Mr Kenny.
"It was good vigilance on the part of our staff member. Gardaí and the defence forces are leading the operation."