The FBI has acknowledged the use of drones to carry out surveillance within the United States. Under questioning by Republican Sen. Chuck Grassley of the Senate Judiciary Committee, FBI Director Robert Mueller confirmed the domestic use of drones, but called it “very seldom.” He also said the bureau is still drafting regulations to address privacy concerns.

Robert Mueller, FBI director: “We are in the initial stages of doing that. And I will tell you that our footprint is very small. We have very few and of limited use, and we’re exploring not only the use, but also the necessary guidelines for that use.”

Sen. Chuck Grassley: “Does the FBI use drones for surveillance on U.S. soil?”

Robert Mueller: “Yes.”

Sen. Chuck Grassley: “I want to go on to a question” —

Robert Mueller: “And I — well, let me just put it in context, though.

Sen. Chuck Grassley: “Sure.”

Robert Mueller: “In a very, very minimal way, and very seldom.”

Sen. Chuck Grassley: “OK.”

In a statement, Democratic Sen. Mark Udall questioned whether drone spying is constitutional, saying: “I am concerned the FBI is deploying drone technology while only being in the 'initial stages' of developing guidelines to protect Americans’ privacy rights. I look forward to learning more about this program and will do everything in my power to hold the FBI accountable and ensure its actions respect the U.S. constitution.”