An airline stewardess struggling to lift her bag at a German airport led to the discovery of a 6-million euro (5.3 million pound) coin fraud.
The customs officer who stopped the stewardess in early 2010 found thousands of one and two euro coins in her bag, Bild newspaper reported in its Thursday edition.
The incident sparked an investigation that has uncovered a forgery ring stretching to China and potentially implicating employees of German airline Lufthansa, the paper said.
The Frankfurt prosecutors' office said on Thursday it carried out dawn raids on offices and residences and arrested six people, four of whom are from China.
It suspects them of having smuggled coins that had been taken out of circulation or bits of those coins into Germany from China, where they had been sent as scrap metal.
The suspects then put the coins back together and exchanged them for a total of 6 million euros at the Bundesbank from 2007 to 2010, the prosecutors said.
Airline cabin crew do not have a weight limit on their baggage, prosecutors highlighted in a statement.
There was no suspicion of any wrongdoing on the part of Bundesbank employees, the prosecutors' office added.
The Bundesbank said in a statement it was aware of the investigation into the use of scrapped coins. It also said that no Bundesbank employees were subject to the investigation.
A Lufthansa spokesman on Thursday said it was aware that individual employees were under investigation, but said the group could not comment on the investigation.
Old euro coins are taken out of circulation by removing the inner part of the coin from an outer ring and thus effectively turning them into scrap metal.
The investigators recovered around 3 tonnes of coin pieces as well as a machine for putting them back together, prosecutors said in the statement.
The Bundesbank is the only institute in Europe that exchanges damaged euro coins for free, replacing them with new ones of the same value.