Former Chairman and Chief Executive of Anglo Irish Bank Sean FitzPatrick has been arrested by members of the Garda Bureau of Fraud Investigation.
Mr FitzPatrick was arrested at his home in Greystones, Co Wicklow, at 6.30am.
Gardaí also searched Mr FitzPatrick's home.
He is being detained under Section 4 of the Criminal Justice Act 1984. His period of detention has since been extended on two occasions and he can now be held until 6.30am tomorrow morning.
Mr Fitzpatrick is being questioned as part of what gardaí describe as an investigation into alleged financial irregularities at a Financial Institution - understood to be Anglo Irish Bank.
It is understood that Mr Fitzpatrick was arrested on suspicion of alleged financial irregularities.
Mr Fitzpatrick stepped down as Chairman of Anglo Irish Bank in December 2008.
Minister for Finance Brian Lenihan has responded to the development by saying: ‘I have always stated there is an extensive Garda investigation under way.
‘I have been cautious not to prejudice that investigation and am eager to see justice take its course.’
There are multiple probes continuing into activities of Anglo Irish Bank.
These are being conducted by the Financial Regulator, the Garda Bureau of Fraud Investigation and the Office of Director of Corporate Enforcement.