The incident is being investigated by three bodies
Irish Rail say several investigations are underway after a DART train experienced a low speed derailment.
It happened north of Dun Laoghaire at around 6:15pm on Wednesday.
There is no report of injuries to anyone onboard.
Customers onboard the train affected were walked back to the nearest station by Iarnród Éireann staff.
Some services were suspended for a time between Lansdowne Road and Dun Laoghaire.
Dublin Bus is also honouring rail tickets during the disruption.
Irish Rail says the line between Lansdowne Road and Bray is not expected to re-open until Thursday, when a full service is expected to operate from first service in the morning.
Services operating between Lansdowne Road & Howth/Malahide and Bray and Greystones only. The line between Lansdowne Rd & Bray is not— Iarnród Éireann (@IrishRail) September 13, 2017
expected to reopen this evening. A full service is expected to operate from first service in the morning, updates will be posted here— Iarnród Éireann (@IrishRail) September 13, 2017
and at irishrail.ie before first service in the morning— Iarnród Éireann (@IrishRail) September 13, 2017
Irish Rail say the company - along with the Rail Accident Investigation Unit and the Commission for Rail Regulation - will be investigating the incident.