An Irishman from the midlands will appear in court in Marseilles today charged with transporting four tonnes of cannabis, with an estimated value of €6.5 million.
He will be imprisoned in Marseilles or Perpignan pending trial and he risks a prison sentence of seven to 10 years in France.
The man, who is in his mid-30s, has no criminal record and has recently set up a small trucking company.
He is believed to have picked up his cargo in southern Spain and was bound for Ireland.
The suspect is described as foolish and "not big-time" and is believed to have transported the drugs for someone else, perhaps unaware of the enormous risk he was taking.
He was arrested at Perthus, on the Franco-Spanish border, by customs officers on Monday, at the wheel of an Irish-registered tanker truck normally used to transport grain.
When customs inspectors opened the trap doors of the tanker, they found sand, which covered 238 packets of cannabis.
French customs seizes one-tonne or greater shipments of cannabis about once a month on average.
Three big seizures have been made in the Perpignan area in the past three months.