The FBI revealed to Sen. Rand PaulRand PaulTrump: 'No doubt' we'll make a deal on healthcare Overnight Defense: General says US strike probably led to civilian deaths | Tillerson to push NATO on spending | Trump taps F-35 chief Senate backs Montenegro's NATO membership MORE (R-Ky.) that it has flown drones in U.S. airspace 10 times since 2006.
In a letter released by Paul on Thursday, Stephen Kelly, the FBI's director of legislative affairs, said that the agency uses drones in "very limited circumstances" for aerial surveillance. None of the drones are armed with either lethal or nonlethal weapons, Kelly said.
Eight of the times the FBI used drones were for criminal cases and two of the times were for national security.
"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.
All requests to use a drone must be reviewed by an FBI legal counsel and approved by senior management. The FBI said it would acquire a warrant before using a drone to obtain any information to which a person would have a reasonable expectation of privacy. But the agency said it has yet to need to ask for a warrant for drone use.
The agency provided additional details to Paul in a separate classified letter.
But the Republican, who staged a nearly 13-hour filibuster earlier this year in protest of lethal drone strikes, said the letters failed to answer all of his questions.
In a follow-up letter sent on Thursday, Paul pressed the FBI for details on its interpretation of a "reasonable expectation of privacy" that would trigger the warrant requirement.