Police are responding to reports of a significant incident at RAF Mildenhall in Suffolk.
A man has been arrested after apparently trying to drive through a checkpoint at the base used by the US air force.
RAF Mildenhall was put into lockdown as police responded to reports of what they called a "significant incident".
A person was arrested and is now in the custody of Suffolk Police.
A US military statement said the base was locked down at 13:00 GMT "following reports of a disturbance" and emergency personnel were deployed.