If so, there are some pretty good reason why, if they consider that threat even remotely real, they should clear the area.
A good indication that the actual terrorist threat is absolutely vanishingly small: If there were lots of terrorists around, one of the easiest targets these days that'd maximize the amount of terror, is airport security screening areas. If they get through, they could defuse the bomb and blow it up on a plane instead, if not, they could let it go off on a timer and take out both a lot of passengers and a lot of security people.