Drone was gathering intelligence when it went down in Iran, U.S. officials say

Controllers reportedly lost contact with the prized stealth unmanned aerial drone last week over western Afghanistan.

The super-secret drone that Iran claims to have recovered was on a CIA "Focal Point" mission, gathering intelligence and likely crashed though it remains uncertain whether it was able to self-destruct, U.S. officials told National Journal on Tuesday.

Controllers lost contact with the prized stealth unmanned aerial drone, the RQ-170 "Sentinel", last week over western Afghanistan, said one government official who spoke on condition of anonymity. Based on its projected glide path, officials assume it fell just inside the Iranian border.

Though the CIA has used the Sentinel to monitor Iranian nuclear convoys before, the precise nature of the mission this time is not known.

The Sentinel is the top-of-the-line UAV, with highly sensitive cryptographic and stealth technology. If it indeed reaches Iranian hands undamaged it will represent a compromise in the latest of U.S. stealth technology, said officials with knowledge of the program.

An investigation is under way and the rest of the small fleet of classified UAVs have been grounded. They number less than 10 and are piloted by the 30th Reconnaissance Squadron at Creech Air Force Base in Nevada.

The drones are thought to be equipped with self-destruct capabilities in the event that they lose contact with their controllers, which is why the U.S. was initially skeptical of Iran's claim to have the drone in custody. The officials didn't say if they knew for certain that the fallen drone had managed to self-destruct.

Near Afghanistan's border with Iran, the U.S. operates non-stealth drones called RQ-7s for counter-narcotics missions. But all of those are accounted for, the officials say.

Every Sentinel mission must be approved by the National Security Staff in advance of its execution and elaborate measures are used to protect it.

The Sentinel achieves stealth due to its wing-like design, high altitude flying and energy redirecting paint. It was created to secretly monitor the proliferation activities of Iran and North Korea.

The cryptographic gear on board is state of the art, as are its sensor packages, which include radiation signature monitoring and advanced hyperspectral imaging.