http://www.11alive.com/rss/article/...-Center?utm_source=dlvr.it&utm_medium=twitter ATLANTA -- Police have shut down Marietta Street in downtown Atlanta between Spring Street and Andrew Young Drive. They have also closed Centennial Olympic Park Drive NW between Georgia Dome Drive NW and Nassau Street NW. Officers are sweeping the CNN Center for any suspicious people or packages following a phone threat from a man who told 911 Operators he was at the location with "a chemical bomb". 11Alive News has crews going to the scene. This story will be updated as more information comes in.