U.S. officials say a drone that crashed inside Iran over the weekend was one of a fleet of stealth aircraft that have spied on Iran for years from a U.S. air base in Afghanistan.

They say the CIA stealth-version of the RQ-170 unmanned craft was also used to survey Osama bin Laden's compound before the May raid in Pakistan.

According to these officials, the U.S. has built up the air base in Shindad, Afghanistan, with an eye to keeping a long-term presence there to launch surveillance missions and even special operations missions into Iran if deemed necessary. The officials spoke on condition of anonymity to discuss classified information.

The officials say that while no specific mission into Iran has been authorized, the military has contingency plans for such clandestine missions.