A rare glimpse at security measures in place at Mall of America

The Mall of America has provided a rare glimpse into security for the nation's busiest shopping center after an online video purportedly produced by a terrorist group urged extremists to attack shopping malls in Western countries.

The Bloomington megamall has some 40 million visitors each year and the behind-the-scenes steps taken to keep visitors safe are generally unknown to shoppers.

Officers patrol the mall with family-friendly dogs trained to sniff out bombs. A security team stationed at a nerve center keeps watch on hundreds of security cameras throughout the shopping center. Delivery trucks are swabbed for explosives before merchandise in unloaded.

Mall officials say most safety measures have long been in place, but that it's stepped up security following the threat.