Police in The Hague have directly connected two Dutch nationals in their early 20s to the killings of the three Irishmen in the city two months ago.
One suspect has admitted he carried out the killings, while the second confirmed he was present in the apartment in Scheveningen, a seaside resort outside the city.
The public prosecutor's office yesterday described the men as a 22-year-old from The Hague, and a 20-year old from Wassenaar, a suburb of the city. It is understood that the three Irishmen who were shot, their bodies mutilated and then set alight, knew their killers.
One of the suspects, who have been in custody for four weeks, has confessed to the triple killing, to setting fire to the apartment and to two other violent robberies in the Netherlands in April.
"In the last of these attacks, people were put under threat from firearms and a certain amount of goods and money were taken from them," according to a police statement yesterday.
The families of brothers Vincent (29), and Morgan Costello (21), from Bansha, Co Tipperary, and Damien Monahan (24), from Ennis, Co Clare, were telephoned on Tuesday night by the officer leading the investigation to inform them of the breakthrough.
A spokeswoman for the public prosecutor's office, Ms Kitty Nooy, said police were not searching for additional suspects. She said both men were known to police, with one of them "well known" to the force.
Ms Nooy said police were currently investigating whether the men were under the influence of drugs at the time of the killings, and the specific role of the second man, who claims to have been a bystander.
According to Ms Nooy there may have been drugs present in the apartment but it was "not very likely" that the deaths were drug-related or linked to a major drugs gang. She added that the mutilations could have occurred after the deaths in an effort by the killers to conceal their identities.
Meanwhile, the detention of the injured English associate of heroin dealer Derek Dunne has been formally extended by a Dutch magistrate because he has nowhere else to go.
Mr Dunne was killed in an armed confrontation at his home in a suburb of Amsterdam at the weekend, after the Englishman was forced to bring an armed gang to the Dubliner's townhouse to repay a debt. The 25-year-old appeared before a magistrate's court in The Hague on Tuesday evening and will now be held for a further 10 days.
A second associate of Mr Dunne, a Dutchman aged 30, seriously injured with gunshot wounds, remains in protective custody in hospital.
Police are still searching for two or three men who fled the scene in a car, but officers believe they have identified the gang.
The two injured men have co-operated with the police investigation, as has Mr Dunne's partner, Ms Rachel Mitchell, the daughter of crime figure, George "The Penguin" Mitchell. Mr Dunne's body has been released to his family for the funeral, which is likely to take place in Amsterdam.