The National Crime Agency confirmed that it has agreed to lead the investigation into sensational claims surrounding the north's Nama property deal.
NCA Deputy Director of Operations Graham Gardner said:
“The NCA has considered a request from Police Service Northern Ireland and has agreed to lead an investigation, calling on support as necessary from PSNI officers. We will not be providing a running commentary on our progress but will provide updates as and when appropriate.”
Police commanders had been coming under intense pressure to intervene following explosive allegations levelled in the Dáil last week by independent TD Mick Wallace.
Last night the PSNI finally launched a criminal investigation into his claims that a £7m offshore fund may have been earmarked for a Northern Ireland politician.
Detectives are to probe the £1.3bn sale last year of assets owned by the Republic's 'bad bank' Nama to US investment firm Cerberus.
Sinn Féin Deputy First Minister Martin McGuinness welcomed the police probe and said a judicial inquiry may need to be established to examine the controversy.
The DUP also welcomed the announcement.
It is understood Britain's National Crime Agency could be involved in the investigation and the PSNI is also set to liaise with An Garda Síochána.
Leading politicians had also suggested a police investigation could involve the FBI because the Nama deal involves New York-based firm Cerberus.
Announcing the investigation, the PSNI's head of crime operations Assistant Chief Constable Will Kerr said officers were engaging with "national and international law enforcement partners".
"We believe that there is sufficient concern in relation to potential criminal activity, surrounding this property deal, to instigate an investigation," he said.
"PSNI are now engaging with a number of other national and international law enforcement partners to consider how best to take forward this investigation."
Mr Wallace's allegations in the Dáil last Thursday related to the role of Belfast law firm Tughans, which carried out work on the Nama deal.
The Wexford TD said money was discovered in an Isle of Man account during a routine internal audit.
Tughans said fees were diverted into an account controlled by former managing partner Ian Coulter without their knowledge and have since been retrieved.
Mr Coulter has not commented publicly on the claims, while Nama and all private firms involved in the assets sale have denied wrongdoing.
Reacting to the PSNI move, Mr McGuinness said on Twitter: "This is very serious, necessary and welcome. Consideration will also be given to the establishment of a judicial inquiry."
A DUP spokesman said: "This is a welcome announcement and the appropriate step to deal with the serious allegations which have been made.
"Indeed, the First Minister called for such action by the authorities last week noting that accusations of criminal behaviour tarnish politics and should be fully investigated.
"We trust everyone concerned will cooperate fully with the PSNI team."
Fianna Fáil leader Micheál Martin also welcomed the PSNI probe but called on the government in the Republic to launch a commission of inquiry.
