Minister for Justice Alan Shatter has said the car found burned out near a forest in Co Armagh is probably the vehicle used by the gang that shot dead Det Garda Adrian Donohoe in Co Louth last Friday evening.
Mr Shatter said investigations were going on to establish a link between the car, a Volkswagen Passat, and the robbery.
"The likelihood is that it was the car that was engaged in the robbery," he said.
"There's still work to be done in that context. I obviously don't want to say too much on some of the detail of the investigation that's taking place. A very intense investigation is taking place and the Police Service of Northern Ireland and an Garda Síochána are working hand in hand, exchanging information and working together to ensure justice is done."
The Minister also said anyone convicted of murdering a member of an Garda Síochána should serve a 40-year sentence without remission, as provided for by the criminal code.
He made his comments after meeting colleagues of Det Garda Donohoe in Dundalk. Mr Shatter described the shooting as an “appalling, callous act”.
In an interview this evening, Mr Shatter told RTÉ's Drivetime that he shared the views attributed to Ann McCabe, wife of murdered Det Garda Jerry McCabe, in which she said killers of gardaí should serve time without remission.
"I believe that any individual who takes the life of a member of an garda siochana they’re not only attacking the individual guard, they are also attacking the entire force and indeed they’re attacking the State and I want to be absolutely clear that a sentence of that nature should apply," he said.
Mr Shatter was critical of comments by PJ Stone of the Garda Representative Association in which he said gardaí were working "in fear and trepidation" and are not getting the support of Government.
"Any issue relating to reforms that are taking place within the Garda Síochána is an issue to be addressed on another day. He well knows, and he should know, that the murder of Adrian Donohoe is nothing to do with issues of resources. He well knows that the Garda Síochana have the full support of the Government.
Det Garda Donohoe (41), a father of a daughter and son aged six and seven, was killed when he was shot at close range in the car park of the Lordship Credit Union, Bellurgan, Jenkinstown, on the Cooley peninsula at 9.30pm on Friday. Based in Dundalk, his wife Caroline is a garda at the same station.
"Everyone is dedicated to ensuring that those responsible for what happened on Friday evening are brought to justice." The Minister said he was "confident those who are responsible for the unspeakable murder that took place will be brought before the courts and justice will be done," Mr Shatter said.
He has signed a book of condolences in the Det Garda Donohoe's Garda station and left a floral wreath with a hand-written card.
It read: "Sincere condolences on the loss of a courageous and young life cut tragically short. Alan Shatter."
The Minister added that he has been in contact with Secretary of State for Northern Ireland, Teresa Villiers.
Garda Commissioner Martin Callinan said no resources would be spared in the search for the murderers. More than 100 officers are involved in the investigation.
The Garda Press Office declined to comment for operational reasons on media reports that the gang left behind a substantial sum of cash.
An Garda has renewed its calls for information around key events on Friday including any suspicious activity near the Lordship Credit Union, Bellurgan, between 6.30pm and 9.30pm, and anyone who saw the Passat found burned out on the Keady to Newtownhamilton Road in Co Armagh yesterday.
Det Garda Donohoe had lived in the Lordship townland and will be buried there on Wednesday after 12.30pm funeral Mass at St Joseph’s Redemptorist Church.
At least five raiders appeared to have very good knowledge of the road network in the area and of the times for the regular Friday night movement of cash from the credit union into Dundalk.
A gang of criminals from north Louth-south Armagh are the chief suspects. This gang raided the post office in 2011 and escaped with just over €60,000 on a Friday night as armed gardaí were about to arrive to escort the cash to a bank night safe in Dundalk.
The circumstances of that robbery are almost identical to last Friday’s raid. However, the investigation is in its infancy and the possible involvement of dissident republicans has not been ruled out. Det Garda Donohoe arrived at the credit union in an unmarked Garda car with Det Garda Joe Ryan, who was driving.
They were there to provide an armed escort for a credit union member of staff who was to drive her car into nearby Dundalk to deposit a bag of money at a bank night safe.
When they arrived at the car park, the two armed detectives realised a vehicle and four men were already waiting there.
Det Garda Donohoe got out of the car to question the men on what they were doing when one of them discharged a shot from a shotgun, fatally wounding him on the right side of his face and head. He was given no warning and had not drawn his sidearm.
The raiders then continued with the robbery, shouting at Det Garda Ryan to stay back and threatening him at gunpoint. They threatened the credit union staff and took a bag with €4,000 before fleeing in their vehicle.
Anyone with information is asked to contact the incident room in Dundalk Garda station at 042-9388400, the Garda Confidential Line on 1800-666-111 or the PSNI on 04890-650222 (from the Republic) or 0845-6008000 (from Northern Ireland).