Updated at 3.30pm.

Services at Heuston are back up and running but subject to delays.

Update: All services to/from Heuston are expected to continue to operate this evening. Some delays on route may occur as signalling issues are ongoing and we work to rectify https://t.co/eAaw8nuXiE

— Iarnród Éireann (@IrishRail) May 28, 2019

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Thousands of commuters have been hit with massive delays today [May 28] after a "major signal fault" impacted a number of Irish Rail services. On Twitter, Irish Rail said that the fault meant there were "no services moving into and out of Heuston." They also advised anyone who has not arrived at the station to look for alternative transport.

Update: Ongoing efforts to rectify the signal fault at Heuston. We are advising all customers who have not yet arrived at a station to seek alternative transport as there are no services moving into and out of Heuston

— Iarnród Éireann (@IrishRail) May 28, 2019

The news first emerged earlier this morning, when a spokesperson for Irish Rail confirmed on Twitter that there were "no services operating into and out of Heuston." They added:

"This includes Newbridge/Hazelhatch to Grand Canal Dock services. DART, Commuter and Intercity services into and out of Connolly are not impacted."

Update: Services to/from Heuston and to/from Newbridge/Hazelthatch/GCD are operating, knock on delays do remain https://t.co/fITkKVA582

— Iarnród Éireann (@IrishRail) May 28, 2019

However, speaking on RTÉ Radio One's Morning Ireland today, Irish Rail spokesperson Jane Cregan said it was "impacting everything from Dublin to Cork and also Dublin to Athlone." She explained that Irish Rail are "hoping to have it rectified as soon as possible," but that there's currently no indication of a timeline for when it will be resolved. She said:

"Everything from Dublin to Cork to Limerick... a train may have got as far as Charleville, the Waterford route may get as far as Kilkenny. "It's the whole signalling system. In reality there is nothing moving in or out of Heuston."