Two Latvian men who were arrested on suspicion of trespassing at an RAF base in Cambridgeshire have been bailed.
The duo, aged 32 and 36, were arrested at RAF Molesworth in the early hours of Thursday and taken to a Cambridgeshire police station.
They have since been released on bail while police continue their investigation.
Commander Helen Flanagan, head of Counter Terrorism Policing London, said there was nothing "so far" to suggest the incident was connected to the events at RAF Fairford last month.
She went on: "Our investigation continues and we are working closely with colleagues from the Ministry of Defence Police and Cambridgeshire Constabulary on this.
"A key line of enquiry remains to identify any potential motivation behind why the men were at that location, and this includes whether it may be connected to any criminal activity.
"Meanwhile, I would encourage the public to remain vigilant and if you see anything of concern, then to contact police."
Ministry of Defence Police (MDP) carrying out security patrols at RAF Molesworth initially found an abandoned vehicle near the perimeter of the base around 10pm on Wednesday.
A small breach of the perimeter fence was then identified and, at around 2am on Thursday, the two men were found and arrested.
Specialist explosive ordnance disposal officers were deployed to carry out additional checks before the vehicle was taken away by officers to be searched.
The two men were initially arrested on suspicion of trespass on a prohibited site and criminal damage.
They were then further arrested on suspicion of an offence under section 4 of the National Security Act - which is "entering a prohibited place for a purpose prejudicial to the UK".
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Officers also carried out two searches at addresses in the Peterborough area as part of the investigation.
RAF Molesworth is home to a NATO intelligence hub and the US's intelligence operations centres for Europe and Africa, according to the Central Intelligence Agency's (CIA) website.
NATO's Intelligence Fusion Centre supports the Supreme Allied Commander Europe and Allied Command Operations - responsible for the planning and execution of the organisation's operations.
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