GARDAI investigating the fatal shooting of major burglar Christopher Warren are expecting to make further arrests in the coming days.
Two men have already been held for questioning in connection with the shooting in Dublin on Friday night.
The latest arrest was carried out by armed detectives yesterday during a search of a house in the Crumlin area of the city.
The 27-year-old suspect was arrested at South Brown Street and taken for questioning about the attack to Mountjoy station.
He is being held under section 50 of the 2007 Criminal Justice Act, which allows gardai to detain him without charge for up to seven days.
A man, who had been arrested in the early hours of Saturday, was released without charge on Sunday night. He was detained after gardai found a Mercedes car, which they believe was used to bring the badly wounded victim to St James's Hospital on Friday night.
Warren was left outside the accident and emergency unit, but died shortly afterwards. He was shot with a handgun in the upper body and was also hit in the lower leg.
Gardai believe that the shooting was a punishment attack that went wrong. Officers think his killers had intended to either assault him or shoot him in the legs but during an apparent scuffle in a car he was shot twice at Constitution Hill in the north inner city before being ferried to hospital.
Meanwhile, officers investigating the fatal shooting of criminal Ned Hamilton in Kilmeague, Naas, Co Kildare, on Saturday may have to wait until the end of the week before speaking to a crucial witness.
The witness suffered severe damage to a thumb during the shooting and is currently receiving treatment at Naas hospital.
Hamilton (33) was hit in the upper body with a shotgun blast while drinking with two other men in a chalet at the rear of a bungalow, located in the rural Kilmeague area.
Gardai have recovered a legally held shotgun and are now trying to establish if it had been discharged accidentally.
Hamilton, from nearby Donadea, was well known to gardai and was suspected of drug dealing. He was an associate of Andrew Barry, one of two men murdered in a gun attack in Kilcock, Co Kildare, last March.