A man is being questioned by police after a disturbance at an RAF base during which shots were fired by US service personnel.
The 44-year-old British man was apprehended at RAF Mildenhall and is being held by Suffolk Police on suspicion of criminal trespass. The incident is not being treated as terrorism.
Superintendent Kim Warner, of Suffolk Police, said a vehicle failed to follow security directions at the entrance and drove on to the base.
There was a "short pursuit" and the vehicle was stopped by US security services, he said.
The man, who suffered cuts and bruises, has been taken into custody and police are not looking for anyone else on the site in relation to the incident.
There were initial reports of a car being rammed into a checkpoint, but Mr Warner said he was "unaware of any damage to the base itself".
He said the vehicle was brought to a halt close to a US plane, an Osprey, and it was not thought there was "any significant damage" to the vehicle or the aircraft.
There was "no obvious motive at this stage", he added.
The base, which is used by the US Air Force, was put on lockdown at around 1.40pm on Monday.
Mr Warner said there would be an internal investigation by the base into the shots fired and the security breach.
Suffolk Police said inquiries were ongoing and officers were receiving support from other law enforcement agencies.
The force said in a statement: "There is no wider threat to the public or occupants on the base and no other people have been injured as a result of the incident."
In November last year the then defence secretary Sir Michael Fallon said RAF Mildenhall was one of 56 Ministry of Defence sites earmarked for closure.
The base, due to shut in 2022, is home to the US Air Force's 100th Air Refuelling Wing and 352nd Special Operations Wing.
It is believed to be home to around 3,000 military personnel and their families, and has previously been identified as a potential target for terrorists.
In May 2016, Junead Khan was given a life sentence at Kingston Crown Court for planning a strike against American military personnel in Britain.
Khan, of Luton, used his job as a delivery driver to scout bases including Mildenhall and nearby RAF Lakenheath the previous year.