Austrian police are investigating how bank notes worth tens of thousands of euros ended up in the Danube River.

The notes were found floating down the river in Vienna on December 5, leading one passer-by to jump in and salvage the money.

According to police, the recovered money was worth some €100,000 ($108,000).

Police also said there were no crimes were recorded in the area and that it was not clear where the money originated.

According to local reports, officers had first believed the money – made up of €500 and €100 notes – was counterfeit, but they now believe the notes to be genuine.

They were first alerted when bystanders spotted a boy in the river on December 5. Fearing he was attempting suicide, they called police, only to find he was trying to retrieve the money.

Anyone who finds money and hands it to police in Austria is entitled to keep between 5% and 10% of the total.

However, if the owner is not found within a year, the whole sum will be handed to the boy.