Cocaine with an estimated street value of €8.4m (£7m) has been seized in the Republic of Ireland.
Two men have been arrested and a Cessna light aircraft has also been seized in County Longford.
Two cars were stopped in the Lough Owel area of County Westmeath shortly after 18:00 local time on Thursday.
Gardaí (Irish police) said it was highly likely some of the 120kg of cocaine would have ended up in Northern Ireland.
Det Ch Supt Seamus Boland told BBC News NI's Evening Extra that organised criminals do not recognise borders and operate on an all-Ireland basis.
He said they were investigating whether the drugs were brought in by private plane and it would not be the first time a light aircraft had been seized as part of a drug trafficking investigation.
"We had a similar incident back in February down in Waterford where a light aircraft was seized in the course of an investigation in collaboration with our UK colleagues, the National Crime Agency," he said.
"That was following a significant seizure of drugs in the UK when the aircraft then flew on and landed here in Ireland.
"It is not new for organised crime - it is something that is experienced across the rest of Europe."
He added they were exploring the aircraft's history and liaising with counterpart in mainland Europe, particularly in France.
After the car was stopped, follow-up searches were carried out at properties in Naas, County Kildare, and Waterford city, as well as at a commercial airfield in County Longford.
Two men aged 54 and 40 were arrested on suspicion of drug trafficking, police said.
Garda Assistant Commissioner Justin Kelly, who is head of organised and serious crime, said the operation "prevented a considerable quantity of dangerous drugs from making it on to our streets and causing significant harm to our communities".
"An Garda Síochána is committed, under Operation Tara, to disrupting and dismantling the organised criminal networks who profit from drug trafficking and impact so negatively on our society," he said.