Cross-Border rail services have been disrupted following closure of the line between Portadown, Co Armagh, and Lisburn, Co Antrim.
Northern Ireland Railways took the decision following advice from the PSNI and closed the line at about 5.30pm on Monday citing a "perceived risk". It is not expected to be reopened before tomorrow.
The Irish Times understands that the decision was taken following the possibility of attacks in the Lurgan area, where the line passes the Kilwilkee estate.
One passenger using the Belfast-Dublin service on Monday claimed the 6pm train took eight hours to reach Dublin.
British army bomb disposal experts carried out a controlled explosion on a suspect device found on the Belfast-Dublin line between Lisburn and Moira. The alert was called off yesterday afternoon.