Gardaí are questioning a man about the murder of gang leader Eamon Dunne, who was shot dead at a birthday party in a public house 2½ years ago.
The suspect, aged 25 years and from Dublin's north inner city, was arrested this morning and taken for questioning to Mountjoy Garda station on the North Circular Road.
He is being questioned about the murder under Section 50 of the Criminal Justice Act and can be detained without charge for up to seven days.
Dunne was shot dead at a 40th birthday party in the Faussagh House pub in Cabra in 2010.
The 34-year-old from Dunsoughly Drive, Finglas, Dublin, was the leader of the State's main drugs gang. He assumed control of the Finglas-based operation when its then leader Martin "Marlo" Hyland was shot dead by his own henchmen in December 2006.
Under Dunne's leadership, the gang had been linked to 14 murders. Dunne had been warned by gardaí his life was in danger. He often wore a bullet-proof vest.
Gardaí believe his murder was organised and paid for by an Irish-led drugs gang based in Spain which has been one of the biggest importers of drugs into the State for more than a decade.
Gardaí are working on the theory that the gang believed the frequency of gun killings being ordered by Dunne was destabilising the underworld in Dublin and damaging the gang's supply route into its main market.
Detectives believe the gang killed Dunne in order to try and calm gangland feuding and bring stability to the Irish drug trade, which was already ailing in the recession as demand for cocaine plummeted.
The man arrested this morning was previously arrested in Ireland as part of the Irish element of an international operation against the Irish-led Spanish-based drugs cartel. A drug dealer, he has been before the courts on drug charges previously.
He was also arrested a number of years ago as part of a Garda inquiry into a major armed robbery involving hostage taking.