Drones of unidentified origin were sighted over three U.S. Air Force (USAF) bases in England during the past six days, a spokesperson for the U.S. Air Force confirmed today.

“Small unmanned aerial vehicles were detected near and over Lakenheath, Mildenhall, and Feltwell bases between November 20 and 26,” the spokesperson stated in an email response to a Reuters inquiry.

Two of the bases are located in Suffolk, while the third is in Norfolk, all leased by the U.S. from the UK.

A British Ministry of Defence spokesperson emphasized that authorities take such threats “very seriously” and maintain “robust measures” at military sites. “We support the U.S. Air Force’s response,” the spokesperson added.