A Dublin socialite was one of three men arrested as €1m in heroin was seized in the city.
The three men were picked up after meetings involving international drug smugglers were watched, the Herald has learned.
The socialite, in his 40s, was held as part of a joint investigation by gardai and UK police into a drug-trafficking ring in Ireland.
He was last night released without charge and a file will be prepared for the DPP.
Gardai are investigating if the massive heroin haul is linked to a west Dublin crime group known as 'The Family' with strong links to Europe.
Three men, including the Dublin socialite, an English/Indian dual citizen and a Turkish drug trafficker, were arrested on Sunday as part of the major operation.
The men were observed at a meeting on Saturday night in Kildare with an associate of 'The Family' gang.
Detectives suspect the meeting was to plan a smuggling operation, and moved on the gang the next morning.
Properties in Meath and Dublin were searched, including a B&B on the southside of the capital where a 7kg haul of heroin was recovered.
The investigation was led by the Drugs and Organised Crime Bureau. The three men were arrested and held at separate Dublin garda stations.
The arrested Irish national was once known in celebrity circles and had a high-profile partner. Sources said he was not under investigation prior to his arrest this weekend.
The English/Indian national arrested is expected to appear before Blanchardstown District Court this morning, charged in connection with the drugs haul.
The Turkish man, aged in his 40s, is considered a major supplier of heroin who arrived in Ireland this year.
The arrests have been described as "highly significant" and the heroin haul is the largest recovered this year.
Detectives believe the drugs are linked to a west Dublin gang known as 'The Family' suspected of being the biggest distributors of heroin in the State.
The crime group has been a priority target for anti-gangland officers, as well as the Criminal Assets Bureau (CAB).
"This seizure of a large amount of heroin is the result of an intelligence-led investigation," Assistant Commissioner John O'Driscoll of Special Crime Operations said.
"This demonstrates the increased capabilities of An Garda Siochana, when working with our international partners, to keep people safe and to target those who would attack our communities with drugs."
In 2017, the CAB seized more than €1m worth of assets from the mob, including luxury watches and high-end cars.
More than 100 gardai and specialist units, including the elite Emergency Response Unit, were involved in 23 raids on properties across the capital, including in Ballyfermot and Clondalkin, as part of the garda crackdown against the major organised crime gang.
In total, €64,000 in cash, 12 luxury watches and 23 high-end cars were seized. A further €312,000 was frozen in bank accounts linked to gang members.
The raids targeting 'The Family' over the weekend were described as "significant".
"This substantial seizure of heroin will help keep our communities and people safe and will impact significantly on organised crime groups involved in the international drugs trade," Detective Chief Superintendent Angela Willis said.