"We continue to work closely with our host nation counterparts to ensure the safety and security of our US service members, US and host nation civilians, contractors, and all of our families," the spokesperson said by email.
Britain's Ministry of Defence said US Air Force Security Forces personnel had responded to reports of unauthorised drone activity and that the situation had been resolved.
"We are working closely with them to establish the facts. We will provide updates in due course," a ministry spokesperson said in an emailed statement.
The US has in recent weeks moved bombers that had been used to strike Iran out of Britain, and relocated huge refuelling aircraft from Britain to Germany. A news report later said there had been a threat from Iran.
The bombers left RAF Fairford on security grounds after a group of men approached the base in white vans in the middle of the night on September 27.
Two men were charged last month in relation to that incident, with prosecutors alleging one of them had tried to assist Iranian intelligence in Britain. The US Justice Department said this week that a member of an Iran-backed militia had plotted to attack the Fairford air base while detained in the US on criminal charges.
Britain's domestic spy chief said in October that Iran had stepped up attempts to hit harder targets such as military sites in Britain.
Tehran has rejected accusations of involvement in the Fairford incident or any other accusations of malign activity in Britain, where the authorities have for a number of years accused it of being involved in plots and attempted assassinations against dissidents and Israeli and Jewish targets.
Germany has blamed Russia for an attempted attack at Leipzig/Halle Airport in August after airport workers found a drone laden with explosives and a detonator at the airport, an important civilian freight and NATO logistics hub in eastern Germany that is also a base for several giant Ukrainian Antonov An-124 cargo planes.
