Tens of thousands of euros have been flushed down the toilet in Geneva, leaving Swiss prosecutors scratching their heads over whether the money is dirty.

Wads of €500 notes were discovered cut to shreds in the sewer system of a branch of Swiss bank UBS, while three more large deposits turned up in the toilets of nearby bistros.

Prosecutors confirmed the notes were worth tens of thousands of euros in total but said they had yet to identify the person who felt flush enough to dispose of the bills.

Swiss investigators said the money appeared to have come from a safe deposit box in Geneva belonging to unidentified Spanish women.

A lawyer for the women appeared at a local police station, according to the Tribune de Genève, but only offered money to pay for plumbing work at the UBS branch and the three restaurants.

“The damage amounted to several thousand [Swiss] francs,” one source told the newspaper, which said the lawyer had not explained why the money had been stuffed down the toilet.

A waiter in the Pizzeria du Molard told the Tribune the restaurant had called the police after the men’s toilets became blocked up. On investigating the cause of the blockage, staff found dozens of shredded €500 in the bathroom’s plumbing.

It is not an offence to destroy banknotes in Switzerland, but a spokesperson for the Geneva prosecutor’s office said the circumstances of the case warranted further investigation.

UBS, which discovered the notes at its branch on the Rue de la Corraterie, declined to comment.