The substance is tested and found to be "baking soda".
Though it is a false alarm, it is still better to be safe than sorry - by erring on the caution side.
Terrorists will be watching. The moment they detect there are sign of complacency, terrorists will pounce and put the "real stuff".
Of course, there will be the problem of "denial of service" where terrorists, or public carelessness or laziness or deliberate sabotage - may cause inconvenience to the public, by arresting such people who cause inconvenience will deter them from such "deliberate or unintentional denial of service".
