Five men were in Garda custody last night after they were arrested following the seizure of cannabis resin worth an estimated €2.5 million.
Three of those in custody were arrested when a car they were travelling in was stopped near Rathcoole, Co Dublin, and 350kg of cannabis resin was found in the vehicle.
In a follow-up operation, six houses were raided in Cabra and Finglas, during which two other men were arrested. Senior Garda sources described the five arrests as "highly significant".
The seized drugs haul is believed to be owned by a Finglas man who is now regarded as one of the biggest drug dealers in the State. However, he was not one of those being held last night.
He is the main target of the National Bureau of Criminal Investigation's (NBCI) organised crime unit, established by Commissioner Noel Conroy last year in response to increased gangland murders and other gun violence.
This man is now the subject of an investigation involving the NBCI, the Garda National Drugs Unit, the Criminal Assets Bureau (Cab), the Garda Bureau of Fraud Investigation and the National Surveillance Unit.
The investigation, called Operation Oak, last month resulted in the seizure of a handgun, rifle, ammunition and a stolen motorbike all linked to the suspect.
A robbery in north Co Dublin linked to the man has also been foiled by the NBCI's organised crime unit. Cab's investigation into the gang leader is well advanced, with boxes of documents having been seized in May from houses linked to the man and a solicitor's office.
Operation Oak was intensified following the murder in Raheny, Dublin, in May of money launderer turned drug dealer Patrick Harte. The 42-year-old, who was originally from Finglas, was gunned down outside his house on the Edenmore estate.
He had flooded the Finglas area with drugs in the months before his death, which had brought down street prices.
The man now being investigated under Operation Oak, who was formerly a friend of Harte's, was unhappy about this. He is believed to have arranged for Harte's murder in order to protect his own drugs business.
Other principals in the gang being investigated under Operation Oak include two men from Finglas who are the chief suspects in a number of multi-million euro cash-in-transit robberies in the last two years.
These men, who were not among the five being held last night, have already been served with combined tax demands by Cab of €400,000.