Police had been tailing the truck, which was carrying a load of tires that had arrived at the port of La Hare Tuesday aboard a ship from Chile.
Bulgarian authorities tipped off the French after the alleged ringleaders of the smuggling operation were detained in Eastern Europe, Radio France Internationale reported.
The cocaine was found hidden among the tires, which were bound for Spain. The two Spanish drivers were arrested.
RFI said it was the largest cocaine seizure ever in France. The previous record was set only last year when 1.3 tons were discovered hidden in suitcases aboard a flight from Venezuela.