Hundreds of angry passengers were forced to wait at Lurgan and Portadown train stations after signal issues caused major delays this morning.
Delays are ongoing and are expected into later this afternoon and this evening.
Translink said: “Due to a major signalling failure there is a bus substitution in operation between Lisburn and Portadown in both directions until further notice.”
A spokesperson for the company said: “Due to a major signalling failure there is a bus substitution in operation between Lisburn and Portadown in both directions until further notice.
“Rail tickets will also be accepted on bus services between these two points. Where possible passengers are advised to make alternative travel arrangements as delays can be expected.
“Translink apologise for any inconvenience caused.”
