A key associate of gangster Paul Rice (52) was arrested during the police operation yesterday and remains in custody.
It is understood that 400 kilogrammes of the drug which was destined for the Irish market was seized in the surveillance operation by Spanish police.
The arrest of the 31-year-old “volatile” Tallaght man is considered “highly significant” as senior sources say that he has become the “effective leader” of the Rice organisation in recent years.
The detained man is well known to gardaí and has a number of previous convictions including for violent disorder and public order offences.
He has served time in jail here and has close links to the Kinahan cartel who also are suspected of having an “active interest” in the massive seized drugs haul.
Last June it emerged that the Rice mob were calling in all drugs debts after a major drugs seizure by gardaí which led to one of their main players being charged before the courts.
The arrested Tallaght man played a major part in this criminal enterprise.
"This is an individual who people are very afraid of he can often be seen travelling around in a convoy of cars and he has been flexing his ¬muscles," a source explained at the time.
"He has been calling in debts by making threatening phone calls and landing at people's doors - the situation seems to have gotten worse since the gardaí had that big success against them, so they must be short of cash," the source added.
Apart from Rice and his younger associate who is now in custody, the organised crime gang consists of two notorious Tallaght criminal brothers and "at least 20 foot-soldiers that range in age from their late teens to their early 30s", according to the source.
The gang is also suspected of sourcing the drugs it sells in the capital from Kinahan cartel operators in Spain.
And they have been using some seemingly legitimate businesses in the Tallaght area to conduct their drug dealing.
In January of this year, a different associate of crime lord Paul Rice had his face "almost sliced off" in a sickening early-morning machete attack in west Dublin.
The man is understood to have required days of medical treatment on his horrific injuries and he refused to co-operate with the garda investigation which was led by officers from Tallaght.
Rice is one of the capital's best-known criminals, but sources say that he had been keeping his head down and was content for his younger associate to "take care of business" on his behalf.
For years, he has acted as an enforcer and debt collector for the Kinahan cartel.
He also has links to a number of dangerous Dublin-based dissident republicans, and was a long-time associate of Gerard 'Hatchet' Kavanagh (44), who was shot dead in an Irish bar in Elviria, Spain, in September, 2014 on the orders of his own gang.
Rice himself is no stranger to violence and he was jailed for 10 years in July 1995 after pleading guilty to the robbery of a bank in which shots were fired.
Back in the summer of 2016 when the Hutch/Kinahan feud, which has claimed 18 lives, was raging out of control, Rice installed new cameras and a state-of-the-art CCTV system in his Dublin home.
In March of that year, he had been officially warned by Gardaí about an active threat against his life after officers received information that the Hutch mob were planning to shoot him.
In October 2014, Rice's home was raided as part of a major investigation by the Criminal Assets Bureau.