The car, carrying several passengers, was stopped Monday at RAF Lakenheath near Suffolk.
Officials of the U.S. Air Force's 48th Fighter Wing, which is based at RAF Lakenheath, didn't immediately return calls, the military newspaper Stars and Stripes reported.
The fighter wing is part of the Third Air Force and is the only F-15 unit based in Europe.
Suffolk police spokesman Nishan Wijeratne confirmed that a vehicle containing several passengers and possibly explosives was stopped at the gate.
Officials established a 1,500-meter "safety exclusion zone" around the base perimeter, Wijeratne said.
Air Force authorities were questioning the vehicle's occupants.
Wijeratne wouldn't comment on the car's passengers, saying everyone was in a "wait and see" mode while the bomb disposal team investigated.