Ongoing chaos in Chicago has prompted extremely tight security on trains in the region. CBS Chicago reports that some trains have been cancelled and others are being swept for bombs out of concern for violence related to the Occupy/Anti-NATO protests taking place in Chicago.

Passenger trains heading south across the Indiana border are being unloaded so that each car can be swept by "bomb-sniffing dogs." Passengers are then loaded on a train which has already been swept before moving on. Individual passengers are also being searched when boarding trains. Food, beverages and large bags are also forbidden while the NATO summit is ongoing. It's not clear if this tough security approach has been prompted by a specific threat.

On Saturday, police announced three men had been arrested in connection with a plot to use Molotov cocktails against political targets, including the President and the home of Chicago Mayor Rahm Emmanuel. Then on Sunday, two more men were arrested on terrorism related charges.

Earlier this month, five men associated with Occupy Cleveland were arrested on charges of attempting to blow-up a commuter bridge near the city. The men had allegedly purchased fake bricks of "C4" from undercover FBI agents and attempted to detonate them using a remote trigger device.