Gangland chief 'Fat' Freddie Thompson remains in garda custody today after being picked up by gardai hours following his return to Ireland.
The Kinahan cartel thug was arrested by armed gardai as part of the investigation into the feud murder of David 'Daithi' Douglas earlier this year.
He was detained by members of the National Bureau of Criminal Investigation (NBCI) as he returned to the capital yesterday afternoon.
It is understood that Thompson (35) flew from Birmingham to Belfast and travelled by car to Dublin, where gardai were waiting for him in the north of the county.
He was being questioned last night at Kilmainham Garda Station over the murder of Douglas (55), who was shot dead outside a shop on Bridgefoot Street in the south inner city last July 1.
He can be held for up to seven days.
The cartel associate has rarely been sighted in Ireland in recent months, and wears a wig when appearing in public.
Sources have revealed that further arrests are expected as part of the investigation into the murder, and that gardai have identified the people involved in Douglas' death.
Father-of-one Douglas was shot six times outside the Shoes-town shop which is run by his wife.
He was a convicted drug dealer and close associate of Darren Kearns, who was shot dead last December in a murder thought to be linked to his role as a drug-money collector.
Kearns' murder is thought to be indirectly linked to the Kinahan-Hutch feud.
Douglas was connected to the Provisional IRA in the 1980s and took part in a post office robbery in Tallaght, during which he fired a rifle at a garda.
He received a 12-year sentence for attempted murder.
Douglas survived an attempt on his life last year when he was shot several times while walking his dog.
Gardai believe he was killed because of his suspected involvement in a botched hit on a Kinahan cartel member.
The attempted hit, which took place outside the Red Cow Hotel last November, saw Kinahan associate Liam Roe, a cousin of Thompson, escape with his life after the gunman's weapon jammed. The cartel suspected Douglas was involved, but gardai are satisfied he was in the north inner city at the time.
Thompson gained notoriety for his involvement in the Crumlin/Drimnagh feud and was suspected of involvement in a number of attacks on rival mobsters.
He is related to a number of other senior cartel members including Liam Byrne (36), whose brother David (33) was shot dead at the Regency Hotel earlier this year.
At one time Thompson was also close to Gary Hutch (33), who was murdered at his apartment on the Costa del Sol in September last year.
Thompson was released from jail in August last year after serving 15 months for violent disorder following an attack on another man at Morrissey's Pub on Cork Street on January 7, 2013.
He had been extradited from Amsterdam in May 2014 and was remanded in custody before he eventually received a 20-month sentence for his part in the brawl.