The FBI has received clearance from federal aviation officials to conduct drone surveillance operations in the United States on at least four occasions since 2010, according to public records and U.S. officials.

The FBI began seeking permission in 2009 from the Federal Aviation Administration to fly drones domestically and received authorization for its first operations a year later, according to documents released Thursday by the FAA.

The documents provide virtually no detail on where the FBI has operated drones in U.S. airspace, for what purpose or how long the missions lasted. But they shed some additional light on the origins and extent of the FBI’s secretive drone program, which FBI Director Robert S. Mueller III revealed Wednesday in Senate testimony.

Mueller told the Senate Judiciary Committee that the FBI uses drones “in a very, very minimal way and very seldom.” He gave no other details, except to say that the agency has “very few” drones and “that our footprint is very small.”

The FBI, he added, is working to develop privacy-protection guidelines, a major concern for lawmakers who worry that drones could be used by the government or private companies to revolutionize spying in the United States.

Paul Bresson, an FBI spokesman, declined to say how many drones the agency has, where they are flown or how many surveillance operations it has conducted. He said the FBI always receives approval in advance from the FAA. “We don’t want to get into how many or the geographic locales,” he said Thursday.

In a statement after Mueller’s testimony, the FBI said it used a drone in Alabama in February during a seven-day hostage standoff. The documents released Thursday show that the FAA granted the FBI permission to fly three other drone operations in 2010 and 2011. The records were disclosed in response to a Freedom of Information Act lawsuit filed by the Electronic Frontier Foundation, a privacy rights group based in San Francisco.

The FAA redacted the vast majority of the text, citing the need to keep law enforcement operations confidential. But the records suggest that in at least one operation, the FBI was flying a Puma AE, a lightweight drone with a range of about six miles. The Puma has a wingspan of eight feet and carries powerful infrared and electro-
optical cameras. It is made by AeroVironment, a California firm.

Drones, or unmanned aircraft, are generally prohibited from flying in U.S. airspace. The FAA has granted special exemptions to dozens of law enforcement agencies and universities, but authorization is generally limited to a confined geographic area and for a fixed period of time.

In June 2012, the Justice Department informed Congress that the Bureau of Alcohol, Tobacco, Firearms and Explosives had six drone helicopters in its fleet and that the Drug Enforcement Administration had “two robotic miniature helicopters,” but made no mention of whether the FBI had any unmanned aircraft.

The Department of Homeland Security flies large surveillance drones along the borders with Canada and Mexico.

Congress has directed the FAA to open domestic airspace to drones by 2015. The agency is developing aviation standards and other safety guidelines for their use.