Five men arrested over an alleged plot targeting RAF Fairford will be released on bail while police investigate whether the incident involved people acting for a foreign state.
Laurence Taylor, the head of UK counter-terrorism policing, said the men remained under investigation after being detained on suspicion of explosives offences and planning a terrorist act.
The suspects, all British citizens in their early 20s and from London, were arrested early on Sunday after a local farmer reported seeing three white vans travelling towards the Gloucestershire air base.
Taylor said the men would be released later on Monday under stringent bail conditions. He told reporters outside London police headquarters: “To be very clear, this does not mean that the investigation is over.”
“They absolutely remain under investigation as we explore multiple lines of inquiry,” he added.
The suspects include a 24-year-old from Camden; three men aged 23, 24 and 25 from Westminster; and a 24-year-old from Willesden.
The material discovered during the investigation was not viable explosives, the Press Association reported.
Taylor said police were examining whether the incident had any connection with the current geopolitical situation, including the possibility that those involved were proxies or individuals knowingly or unknowingly working on behalf of a foreign state.
A source familiar with the investigation said an Iranian-linked motive was considered the most likely possibility, although Russian sabotage and a jihadist plot were also being examined.
Iran’s embassy in London rejected the suggestion of Iranian involvement, saying it “categorically rejects and strongly condemns the recent unfounded and malicious speculations”. It said the claims would fuel “Iranophobia propaganda” in the UK.
Iran’s Revolutionary Guards said in July that RAF Fairford was a legitimate target. The base houses US bombers that fly missions against Iran.
Police were alerted after a farmer reported seeing a group of “hooded and masked men” running into fields. She said she believed her call to the 999 emergency hotline had foiled a plot and that she may have seen as many as 10 people at the scene.
Defence minister Wes Streeting said the farmer had only a “partial picture” of the investigation. He told Times Radio that the Government would provide information about the suspects and the nature of the threat “as and when we can”.
The arrests were not intelligence-led, according to the source familiar with the investigation, meaning authorities had not known in advance that a plot was taking place.
The three vans have undergone extensive examination with support from the military and forensic experts. Taylor said significant police resources remained deployed at the scene.
A 400-metre cordon was imposed around RAF Fairford and residents of 85 homes in nearby Whelford were temporarily relocated.
Interior minister Shabana Mahmood said the scene was safe following work by the Army’s explosive ordnance disposal team and that Whelford residents would shortly be allowed to return home.
US President Donald Trump said on Sunday that the suspects had been seeking to cause “big damage” and had been under investigation by UK and US authorities. Questions were subsequently raised in British media about how closely they had been monitored, given their proximity to the base.
The US embassy issued a security alert after the arrests, advising American citizens to exercise caution and remain mindful of their personal security.
The US Air Force said personnel at RAF Fairford remained vigilant but would not discuss specific force protection measures for operational security reasons.
Prime Minister Andy Burnham was due to chair a meeting of the Government’s emergency response committee, Cobra, later on Monday.
