The letter to Paul, R-Ky., in which Stephen Kelly, the FBI's director of legislative affairs, said the agency uses drones in "very limited circumstances" for aerial surveillance, was released Thursday, the Washington newspaper The Hill reported.
Eight uses of drones were in criminal cases, and two in national security matters. At no time were the drones equipped with weapons, Kelly said.
The agency added a drone was used earlier in the year to support the rescue of a boy, 5, held hostage in an underground bunker in Alabama.
"The FBI does not use [unmanned aerial vehicles] to conduct "bulk" surveillance or to conduct general surveillance not related to an investigation or assessment," Kelly wrote.