Irish Rail Intercity and commuter services to and from Heuston station were unavoidably suspended early this morning after a tragedy on the line in Kildare overnight.
The driver of an empty train to Portlaoise spotted a body on the line between Sallins and Newbridge at around 11pm last night and alerted authorities.
The line was then closed at the request of gardai and Irish Rail also began an investigation to establish how the incident occurred.
But it quickly became clear that somebody had been hit by a train in what is being seen as a personal tragedy.
The line between Sallins and Newbridge remained closed early this morning and did not open until shortly after 8.30am.
Commuters were informed that there would be some "knock-on" delays following the severe disruption.
Intercity services from Galway, Cork, Limerick, Westport and Kerry terminated at Kildare station while the line was closed, and road transfers were in place from Kildare to Dublin.
And a shuttle service from Sallins to Heuston was scheduled to depart every 30 minutes - although a number of commuters reported delays regarding this service.