Spanish police boarded a sailboat from Martinique on December 27, found 740 kilos of cocaine and arrested two sailors.
Law enforcement officers also held two men considered key drug trade players in Nantes and Saint-Denis, France.
Investigators suspect the men are vital links in France for the drug trade involving Paris, Venezuela and Spain.
At the home of one of the men, the investigators seized 390 kilos of cocaine and 25,000 euros in cash.
A Magistrate placed both men in pre-trial detention as investigations continue.
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