Securing America: Iran Scoping Out U.S. Sites?

Has Iran been conducting surveillance in the United States?  A hearing on Capitol Hill took a look at the possible threat posed to the U.S. by Iran and Hezbollah, which killed more Americans than any other terrorist organization before the 9/11 attacks.

FOX News Radio's Lisa Brady reports in our ongoing series on national security:

Audio clip:

(Silber) "We are concerned."

...The NYPD's Head of Intelligence Analysis telling Congress at least 13 people with ties to Iran's government have been questioned since 2005 after taking pictures of New York landmarks and other things, including railroad tracks and a heliport.  Mitchell Silber, echoing what the Director of National Intelligence has said, that some in Iran may be growing more likely to attack in the U.S. 
(Silber) "Either because of hostilities that break out, or the perception of pressure on Iran, that we may be moving forward to a higher likelihood of terrorist activity in the Homeland."
Homeland Security Chief Janet Napolitano says threat information is constantly monitored, and updates given to state and local officials.
Lisa Brady, FOX News Radio.