They estimated the total value of the notes at more than $11 million.
Police staged two raids this week and found a print shop hidden behind a false wall and under a concrete slab in a village between the towns of Meaux and Chelles, east of Paris, Radio France Internationale reported Thursday.
While dozens of people have been arrested for distributing the cash, the source had not been discovered until now. Police did not identify the master counterfeiter but said he was a man in his 50s with a criminal record for counterfeiting.
Between 30 and 40 fake-money rings are broken up annually in France, the highest number in the European Union, but this case was regarded as the biggest ever in France, RFI said.