"The explosives detector was alerted by a laptop, and as a result should have been checked again.
"But at this point the male passenger left the security area into a secured area.
"Searches are still taking place for this person. In the meantime we have examined security camera footage."
Airports around the world have been on high alert since a Nigerian man was arrested and accused of trying to blow up an airliner over the US on December 25 with explosive chemicals.