The first blockage was reported at a UBS, followed days later by three nearby bistros who found their facilities bunged up with €500 notes, the favourite of Europe’s flourishing black economy.

Vincent Derouand of the local prosecutor’s office said it’s not a crime to throw money away or block a toilet, adding: “We are not so interested in the motive but we want to be sure of the origin of the money.”

The prosecutor’s office also said two people had agreed to compensate the restaurants for the costs of the blockage.

The cash was confiscated during the investigation and it was unclear who would get it if it was found to be lawful.

The European Central Bank last year decided to discontinue the €500 note because of concerns about its use in money laundering.