The Royal Air Force Lakenheath base houses the USAF’s 48th Fighter Wing.
London CNN  — 

Unidentified drones have been spotted flying over three bases used by the United States Air Force in Britain, the two countries have confirmed.

The objects were seen between Wednesday and Saturday flying over the Royal Air Force’s Lakenheath, Mildenhall and Feltwell bases, all used by the US Air Force (USAF).

“Installation leaders determined that none of the incursions impacted base residents or critical infrastructure,” a spokesperson for the US Air Forces in Europe said in a statement.

There were about five to six drones, and their activity appeared coordinated, according to a source familiar with the matter. US defense officials are still investigating their origin, but they did not appear to be hobbyist drones, the source said. At no point did they pose a threat to the bases, and there is no evidence they were able to collect any sensitive intelligence, the source added.

A spokesperson for Britain’s Ministry of Defence said: “We take threats seriously and maintain robust measures at defence sites. This includes counter-drone security capabilities.”

Both nations said they would not comment further.

The three bases are located within a few miles of each other in eastern England. Since 1992, Mildenhall has been home to the only permanent American wing in Europe that conducts air refueling operations, while Lakenheath houses the USAF’s 48th Fighter Wing, which has played a role in post-9/11 operations in Afghanistan and Iraq.

In 2017, a car attempted to ram the entrance to the Mildenhall base, resulting in shots being fired by US personnel and the base being briefly locked down.

CNN’s Paradise Afshar contributed reporting.