Police in Dublin were granted extra time to question two men after they were arrested following the discovery of a massive cache of Semtex in the city.
Gardai seized the plastic explosive after armed officers stopped a taxi in the Ballybough area at about 6pm on Friday.
The BBC was reporting on Sunday that Gardai believe the explosives were destined for use in Northern Ireland.
A bomb disposal unit was called and police arrested two men at the scene.
Gardai detained two men, aged 21 and 28, who are being questioned by detectives after their period of detention was extended on Saturday evening.
Police also arrested a third man, aged 55, during a search later on Friday evening in Dublin, and all three are being questioned under the Offences Against the State Act.
The men were arrested as part of an operation into the activities of dissident republicans.
According to the Herald, 6kg (13.2lb) of Semtex was recovered, along with detonators.
The newspaper said one of the men arrested has close links to the New IRA and the military-grade explosives had been sourced in recent weeks.
Doug Beattie MC MLA, the Ulster Unionist Westminster candidate for Upper Bann, said: “Given the devastation caused by semtex in the past, and the despicable and reckless use of explosives by republican bombers – not least in Omagh in 1998 – it is clear to me that lives have been saved by this seizure.
“I commend the Garda for their excellent work.”