The two Travellers -- who are originally from the Rathkeale area of Co Limerick -- and their Polish driver remain in police custody as investigators there try to establish why they were travelling to France with the huge fake cash haul.
The rhino-horn gang, whose senior members are all Travellers from Rathkeale, are a major target for Europol's organised crime unit and they have criminal connections all across Europe, Australia and the US.
French police have been investigating if gang members are linked to the gun murders of two unidentified men who were discovered shot in the head and wrapped in plastic bags in a southern French town in November, 2010. Sources believe that these men had been working for the gang who are also involved in dodgy tarmacadam scams across Europe. The gang, nicknamed the Rathkeale Rovers, has developed a sophisticated network of agents and money-laundering vehicles to sell stolen horns and conceal the proceeds of those sales, which can reach up to €200,000 per horn.
The rhino horn is much sought after across the world for decoration, in the production of luxury goods and in traditional medicine, including Chinese medicine. Trading in rhino horns is illegal under UN laws as they are endangered species.
Last summer, the Rathkeale Rovers were suspected of raiding thousands of euro worth of rhino horns from museums in Belgium and France. The valuables were stolen during break-ins at a natural history museum in Brussels and from a collection in Ile d'Aix off France's west coast in July.
The Brussels theft followed a similar but failed break-in attempt in the southern Belgian city of Liege.
There have been no known robberies of rhino horns in Ireland but in January 2010 customs officers confiscated 10 rhino horns at Shannon Airport, suspected of being smuggled by the Rathkeale Rovers.
Meanwhile, sources have revealed that the two Irishmen were arrested by police in Chancy, Switzerland, on March 23.
They were in a van driven by a Polish national. Around €120,000 in counterfeit notes was found in the van when it was searched by police.
The three men were arrested and remain in custody. It is understood the two Irishmen told police they did not know the Polish van driver, and had simply 'thumbed' a lift with him and were heading towards Lyon in France to go on holiday.
However, police do not believe this story. Police suspect that the Polish van driver was working for the two seasoned criminals. Gardai in Ireland have been contacted by the Swiss authorities over the arrests.