Authorities in Northern Ireland said Thursday that militants with the Irish Republican Army (IRA) planted a bomb on a truck that was intended to explode around the time the United Kingdom left the European Union (EU) on Friday.

A Belfast newspaper had received a call on the day of Brexit saying there was a bomb on a truck at the Belfast docks, according to the Police Service of Northern Ireland. The caller said the truck was headed for a ferry to Scotland.

Despite a search, nothing was found.

Another call was made to the same newspaper Monday with new information. After a daylong search, police found a bomb aboard a truck in the Northern Ireland town of Lurgan.

Police Assistant Chief Constable George Clarke said the caller told authorities "the intention had been for that device to explode on Friday evening at around the time the United Kingdom left the European Union."

The bombers apparently picked the wrong truck, because the explosives-laden vehicle remained at a haulage company's yard in Lurgan until it was discovered.

Police said they believed the bomb plot was the work of a group of pro-Irish militants known as the Continuity IRA.

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"Once that device had left that yard, if it had ... it was exposing people on the public road, at a busy time, and at busy places, to huge levels of risk," Clarke said. "These people are absolutely callous and reckless in what they have done."

More than 3,700 people died during decades of violence before Northern Ireland's 1998 Good Friday peace accord. Most militants have renounced violence, but small groups of IRA dissidents continue to carry out occasional bombings and shootings.

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The violent dissidents were emboldened by several years of political drift in Northern Ireland, whose power-sharing government was suspended between January 2017 and last month -- and by uncertainty about the future of the currently invisible border between the U.K.'s Northern Ireland and EU member Ireland after Brexit.

The Associated Press contributed to this report.