Gardaí yesterday seized heroin with a street value of €3.2 million as part of a major international investigation.
The seizure was made near the village of Collon, Co Louth.
The drugs haul was part of an ongoing intelligence-led operation involving the Garda national drugs unit, Dutch police and the Police Service of Northern Ireland.
Gardaí said three arrests have been made, two in the Republic and one in the North.
The two people arrested in the Republic are aged 45 and 27 and were being held at Navan Garda station under the provisions of Section 2 of the Criminal Justice (Drug Trafficking) Act.
The PSNI arrested a 43-year-old man in Banbridge for questioning.
Three vehicles were also seized in the operation.
In a statement, the Garda said the seizure was made by its national drugs unit, supported by the crime and security unit and officers from the Louth/Meath division.
Det Chief Insp Garry Clarke of the PSNI's drug squad said: "This is a good example of how police organisations working together can reduce the harm which drugs cause to people on the island of Ireland."