Flaking euro banknotes at the center of a German police investigation may have been tainted by drug users, the German news magazine Der Spiegel said on Saturday, offering the latest theory on why some of the normally robust bills have started becoming brittle and falling apart.
It said police and Germany's central bank were examining whether a drug known as "crystal speed" could react to human sweat on the hands to form the sulfuric acid which is directly to blame for the weakening of the paper.
Earlier this month it was disclosed that Germans had handed in 1,500 banknotes since June that had fallen apart when handled. With 10.5 billion euro notes currently in circulation, inferior-quality bills are still very rare, however.
Spiegel said the theory was that the money became soiled when banknotes were rolled up to make tubes for people to snort crystal speed. Crystal speed, which is mainly manufactured in eastern Europe, is often contaminated with sulfates.
The magazine said it was conceivable that the contaminants could react to sweat.
Police leading the inquiry in the city of Mainz and the central bank declined to comment on the Spiegel report, but police in Berlin said there was still no evidence that the money had been deliberately damaged by a criminal act.
"We don't comment on speculation," said a Bundesbank spokesman when questioned about the drug use theory.
Among earlier theories were that the money might have been rubbed with solvents by thieves after it had been cancelled and stamped, or that it might have been tainted by mechanisms inside automated teller machines. Some bills have started becoming fragile, like ancient Egyptian papyrus.