The PSNI chief constable has said he believes that cash uncovered by the Garda in Co Cork in February came from the Northern Bank robbery.
Hugh Orde also said he is hopeful of "developments" in the Robert McCartney murder case in the near future.
Speaking after a public meeting of the Policing Board in Derry, Mr Orde referred to the robbery and to the arrests early on Tuesday of two men in relation to the McCartney murder case. The murder investigation was "work in progress", he said.
Referring to the investigation into the Northern Bank robbery, Mr Orde said he and his senior officers were convinced that sterling notes uncovered by the Garda in Co Cork were linked.
Despite no such statement from the Garda, Mr Orde said he stood by that assessment following consultation with his senior officers.
Commenting on the scale of the investigation, he said: "This is going to take some time."
Sam Kinkaid, head of the PSNI crime branch, said more than 3,000 lines of inquiry were still live, and there was continuing close co-operation with the Garda, the Cab and the North's Assets Recovery Agency.
Mr Kinkaid told the board: "We strongly believe, and I emphasise, we strongly believe that the money recovered in Co Cork came from the Northern Bank robbery and was moved into the Republic of Ireland as part of an IRA money-laundering operation."
In his most positive assessment of the McCartney case to date, Mr Orde said the arrests demonstrated what he called "our absolute commitment to bring this to a judicial conclusion".
"It's what we want. It's what the family wants. It will be in accordance with the law," he added.
Although he resolutely refused to give any details about the questioning of the two men he said: "Hopefully we will see some developments in the near future."
The 19-member Policing Board, which runs the Police Service of Northern Ireland, as well as members of four District Policing Partnerships from the Co Derry area, were told that following Mr McCartney's murder in Belfast on January 30th the investigating team believed IRA members were involved but that it was not sanctioned by the organisation.
The board heard that, before the latest arrests, all 13 suspects arrested to date had remained silent when questioned. The Policing Ombudsman's office had helped witnesses unwilling to approach the PSNI directly to provide 10 statements and three "clarifications" as well as one video statement. The board was also told that, although there had been no specific complaint of intimidation by Mr McCartney's sisters, two incidents were being investigated.
One threat to burn the sisters from their homes was blamed on criminal elements while a second threat emanated from paramilitaries, the board heard.
Senior PSNI officers also updated the board in relation to the Enniskillen Poppy Day bombing of 1988 and the 1972 Claudy bombing which is being re-examined by police.
Mr Kinkaid said he was hopeful of providing closure on the case to the Claudy families and suggested there was perhaps a month or two of major investigative work left in the case.
Unionist members of the Policing Board reacted with some alarm to plans to close some 17 small, mostly rural police stations across Northern Ireland.
However, Mr Orde said the PSNI was tasked with providing an efficient police service and this would be best served by putting more officers on the beat and not having them staffing small stations.
The chief constable, in the face of criticism about plans to introduce a new form of plastic bullet, said the Patten recommendations called for a less lethal alternative to plastic bullets.
"There isn't one," he said. "Success for me is that we don't fire them."