A body scanner at Amsterdam's Schiphol Airport would not necessarily have detected the explosives which the would-be syringe bomber, Umar Farouk Abdulmutallab had sewn into his underwear. A Dutch military intelligence source told De Telegraaf newspaper that Al Qaeda has its own security scanners and has been practicing ways of concealing explosives.

The terrorist group has even carried out test runs at smuggling explosives through European airports, the paper reports.

On Monday Schiphol's operational manager Ad Rutten said the explosives carried by the 23-year-old Nigerian Abdulmutallab may well have been detected had he been scanned by one of the airport's 15 body scanners. Schiphol was the first airport to run a trial of body scanners, which use sound waves to see through passengers' clothing. At present the scanners are only an optional alternative to the conventional metal detector, as European privacy laws prevent them being made compulsory.

Since the attempted attack on the flight from Schiphol to Detroit, Schiphol has been operating tightened security measures. Around 50 extra security staff have been hired in to carry out the tightened checks on passengers to the United States. All passengers to the US are now being body searched at the gate. The airport says that while the chance of discovering any concealed explosives is still not 100 percent, it is at least much higher than it was.

Passenger undergoes body scan at Amsterdam's Schiphol Airport - ANP