FBI Director Robert Mueller acknowledged the law enforcement agency uses drone aircraft in the United States for surveillance in certain difficult cases.

Mueller told the Senate Judiciary Committee on Wednesday that drones are used by the FBI in a “very, very minimal way and very seldom.”

He did not say how many unmanned surveillance vehicles (UAVs) the FBI has or how often they have been used.

But a law enforcement official told CNN the FBI has used them a little more than a dozen times but did not say when that started. The official said drones are useful in hostage and barricade situations because they operate more quietly and are less visible than traditional aircraft such as helicopters.

The FBI said it used a UAV earlier this year to monitor the situation where a boy was held hostage in a bunker in Alabama.

Bureau spokesman Paul Bresson said their use allows “us to learn critical information that otherwise would be difficult to obtain without introducing serious risk to law enforcement personnel.”

Bresson said the aircraft can only be used to perform surveillance on stationary subjects and the FBI must first get approval from the Federal Aviation Administration to fly in a “very confined geographic area.”

Source: CNN