Varying denominations of euro currency have been disintegrating and German police are baffled.
The notes are believed to have come into contact with sulphuric acid - perhaps during a cleaning process, police spokesman Michael Maasz said.
Hundreds of the brittle notes have appeared in at least 17 German towns and cities, German media report.
The popular German daily Bild says a blackmail attempt is one of the possibilities that police are investigating.
The paper says the banknotes are not forgeries.
If I had disintegrating money in my wallet, I would march right to the bank and demand replacements, plus interest.
