Passengers today demanded urgent tests on all railway bridges around Ireland after a viaduct on one the country's busiest routes collapsed into the sea.
Rail Users Ireland said it was a miracle people were not killed when part of an embankment holding track slid into the Malahide Estuary, in north Dublin.
After the landslide at around 6pm yesterday evening, a 20-metre section of rail line on the main Dublin to Belfast route buckled under its own weight.
A train driver spotted the damage during the busy Friday evening rush hour and managed to stop just in time to avoid a serious incident, said Iarnrod Eireann.
Serious disruption is expected on the cross-border line, which will be closed for several weeks.
Mark Gleeson, of passenger organisation Rail Users Ireland, said the collapse raised serious questions about the maintenance and inspection regime on Ireland's rail network.
"This viaduct carries some of the busiest commuter trains in Ireland, it is nothing short of a miracle that the collapse did not result in a serious accident and loss of life," he said.
"While we await the report from the Rail Accident Investigation Unit, it is essential that all bridges are inspected nationwide to ensure no critical faults have been overlooked.
"At this moment, it is extremely important not to be complacent."
Mr Gleeson also demanded cash refunds for all weekly, monthly and annual ticket holders who can no longer travel by train because of the closure.
Iarnrod Eireann said a full investigation has been launched.
Northern commuter services and trains to Belfast will be seriously disrupted.
A shuttle rail service has been put in place between Drogheda and Skerries north of the landslide.
Replacement bus services are also running between Dublin and stations north of the city.
The Belfast Enterprise service will only run between Belfast and Drogheda, with bus transfers in and out of the capital.
Iarnrod Eireann said local Dart services between Malahide and Howth Junction have resumed, and are operating normally.