A 25-year-old dual UK-Iranian national arrested on suspicion of preparing terrorist acts in connection with an incident near RAF Fairford has been released on bail, British counter-terrorism police said Saturday.
The man was detained in Westminster on Thursday as investigators examined events near the Gloucestershire air base, which is operated by the US Air Force.
Police said searches of two properties in London had concluded, while the wider investigation remained ongoing.
The inquiry began after three suspicious vehicles were reported near RAF Fairford in the early hours of last Sunday, prompting authorities to declare a major incident and evacuate dozens of nearby homes.
Five British men aged between 23 and 25 were arrested near three vans on suspicion of explosives offences and later on suspicion of preparing a terrorist act.
All five, who are from London, were subsequently released on police bail under stringent conditions.
Investigators said petrol was discovered inside the vans but that no improvised explosive device was present.
The BBC reported that one of the men had called emergency services about an hour before a local farmer alerted police to a group of masked men near the vehicles.
Counter-terrorism police have described the investigation as complex and said they are examining whether a foreign state was involved.
Prime Minister Andy Burnham chaired a Cobra meeting following the incident and later said there were strong indications of possible Iranian involvement, without providing further details.
US President Donald Trump said there had been a plan to cause major damage at the base, while Secretary of State Marco Rubio said the incident clearly involved a foreign actor.
Iran has rejected allegations of involvement as baseless and summoned the British ambassador in Tehran over the issue.
The Iranian embassy in London also rejected speculation connecting Tehran to the incident.
RAF Fairford has been used by US bombers operating in the Middle East, including aircraft involved in operations against targets in Iran.
The investigation remains active following the release on bail of all six men arrested in connection with the incident.