The weekly Welt am Sonntag, quoting a police report, said 35 percent of the 730,000 passengers checked by the scanners set off the alarm more than once despite being innocent.

The report said the machines were confused by several layers of clothing, boots, zip fasteners and even pleats, while in 10 percent of cases the passenger's posture set them off.

The police called for the scanners to be made less sensitive to movements and certain types of clothing and the software to be improved. They also said the US manufacturer L3 Communications should make them work faster.