Irish police are to continue questioning seven people arrested in an operation against money laundering and illegal fund-raising by the IRA.
More than £26m was stolen from the Northern Bank
They were arrested in Cork and Dublin in a series of raids in which more than £2.3m was seized, including £60,000 in notes from the Northern Bank.
Detectives are examining a possible link with December's £26m robbery at the Northern Bank in Belfast.
Police have said the IRA was behind the robbery - an accusation it denies.
It is understood one of those being questioned is a former Sinn Fein elected representative.
It has not been confirmed if the raids are connected to the Northern robbery.
Two men were arrested on Wednesday night during house raids in the Douglas and Passage West areas of Cork.
Another three men were also detained at Heuston train station in Dublin. It is understood that two of the men are from Londonderry and the third is from Cork.
A man and a woman were arrested in a follow-up operation in the Farran area of Cork on Thursday morning.
Searches took place in the Leinster area on Thursday night.
Garda Inspector Ray McHugh said the police operation, which involved 100 officers, was significant and still evolving.
"There is a lot of work still going on, including forensic work," he said.
"We certainly wouldn't be in a position, or be prepared to say, who we were targeting."
The suspects, who are being detained under Section 30 of the Offences Against the State Act, can be held for 72 hours before they are charged or released.
The money which was seized in Cork is being transferred to Dublin, where it will be examined by the Garda Technical Bureau.
Martin McGuinness said he was unaware of the arrests
Sinn Fein's Martin McGuinness said he would make no comment on the matter until he had more information.
He said there had been previous reports of Northern Bank notes being found and those reports had been false.
A Sinn Fein spokesman said people should not jump to conclusions over the arrests.
"Over the last four weeks we have seen people rush to judgement time and time again," he said.
"We would urge people to exercise caution on this occasion and allow the truth to come out."
The party's leadership has said they believe IRA denials that it did not carry out the bank robbery.
Assistant Chief Constable Sam Kincaid, who has been in charge of the Northern Bank investigation, was in Dublin on Thursday for meetings with senior Garda officers.
It is understood the raid was high on the agenda for the discussions.
A police spokesman in Northern Ireland said it was too early to say whether or not the arrests were connected to the robbery.
"The PSNI is working closely with An Garda Siochana as we have done since the start of the investigation," he added.