Police have confirmed that security checks took place on trains between Belfast and Dublin on Wednesday afternoon.
Officers from the Police Service of Northern Ireland and An Garda Síochána conducted the "precautionary security checks" on March 30.
It followed information suggesting that a "device of some description may have been left on one of the trains."
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However, a statement confirms that "at this stage nothing untoward has been found."
A spokesperson for the PSNI continued: "We apologise for any inconvenience this may cause to passengers however we will never ignore anything that would put members of the public at risk.
"Police would ask anyone who sees anything suspicious to contact them on 101. A report can also be submitted online using the non-emergency reporting form via http://www.psni.police.uk/makeareport/ or through Crimestoppers anonymously on 0800 555 111 or online at http://crimestoppers-uk.org/."
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