The railway line between Portadown and Lisburn has been closed both ways because of a police incident.
Police, along with Translink, are advising passengers to expect delays and disruption to services along the line, including trains to and from Newry, Bangor and the Enterprise service between Belfast and Dublin.
The exact location of the incident is the Ballinderry Road in Lisburn, within the vicinity of the railway bridge.
Diversions are in place and drivers and pedestrians are advised to avoid the area and seek an alternative route.
Translink have also said their services are currently operating as follows: Passengers for Moira, Lurgan and Portadown – may avail of a bus substitution from Lisburn station; between Lisburn and Belfast all stations are still being served. Passengers from Portadown, Lurgan and Moira towards Belfast may avail of bus substitutions to Lisburn for onward rail travel.
There are no further details at present.