Security surrounding a US delegation led by senior Congressman Richard Neal has been stepped up considerably after loyalist paramilitaries were leaked details of his private itinerary.
Congressman Neal is leading a US delegation who are speaking to officials on both sides of the border about the Brexit Protocol impasse.
The senior Democrat’s itinerary for his Northern Ireland leg of the visit was only shared with a small group of people, including senior NIO officials, members of the PSNI involved in providing back up security, and Mr Neal’s own entourage.
Members of the press were not given details of his planned private meetings during his visit to Northern Ireland.
However, the Belfast Telegraph was alerted on Tuesday evening that precise details, including estimated travel times to and from venues, had somehow fallen into the hands of loyalist paramilitaries.
An investigation is now expected on both sides of the Atlantic to discover how the information managed to leak into loyalist hands.
The PSNI and US Government were informed of the security breach on Tuesday evening.
Security for the visit was already high given the recent attack on Irish Foreign Minister Simon Coveney.
Mr Coveney was forced to flee a peacebuilding event in north Belfast in March after the UVF hijacked a van and forced the driver to transport what turned out to be an elaborate hoax device to the Houben Centre in Ardoyne, where the event organised by the John and Pat Hume Foundation was taking place.
Unionists have expressed anger at Mr Neal’s visit claiming he is not fully understanding of unionist concerns around the protocol.
The UK Government has threatened to introduce legislation unilaterally that will override parts of the protocol.
The US Government has warned that any action that endangers the Good Friday Agreement would damage the prospects of any future trade deal between Britain and the US.
On Tuesday, Mr Neal said the dispute appeared to be "manufactured".
Speaking after a meeting with Mr Coveney he said: "I have on this delegation people who are experts at trade and they also would confirm that they think these issues on the trade front, if that's really the dispute, could be ironed out quickly”.
The congressional delegation also met Irish President Michael D Higgins who thanked him for his "informed and careful comments" about the complexities of Northern Ireland.
However, Sir Jeffrey Donaldson responded by accusing Mr Neal of “ignoring the totality of unionist opposition to the protocol" adding that he exposed “his own ignorance and prejudice and slavish adherence to Sinn Fein dogma".
It is not yet known if Mr Neal’s plans for his visit will be forced to change given the seriousness of the security breach.
He was due to spend Wednesday and Thursday in Northern Ireland.
PSNI Assistant Chief Constable Alan Todd said: “It is a long established policy of police not to comment on the security arrangements made for individuals. We routinely work with visiting Heads of State and other key figures visiting Northern Ireland and when appropriate, make full provisions for their safety in line with their requirements.”