UK Arrests Sixth Person in RAF Fairford Security Investigation

British police arrested a dual U.K.-Iranian national Thursday on suspicion of plotting a terrorist attack, widening an investigation into suspicious activity near an air base used by U.S. bombers. Prime Minister Andy Burnham says there are “strong indications” Iran played a part. Tehran denies involvement.

The 27-year-old man was arrested in London, where officers also searched two properties, Counter Terrorism Policing said. Police interviewed a 26-year-old British national “under caution,” meaning the recorded interview could be used in a future prosecution.

The arrests follow a Sunday incident near RAF Fairford, about 100 miles west of London. Police detained five British men in their early 20s from London on suspicion of explosives and terrorism offenses after reports of suspicious activity, including three oddly parked vans and a group of hooded, masked men. All five were released on bail Monday. Police later said they had found petrol in the vans but no explosives.

Fairford has been used by American bombers in conflicts in the Middle East, including the war with Iran. Iranian authorities have warned that bases used to attack their country would be considered legitimate targets.

Burnham told the BBC that “there are strong indications that Iran played a part in what happened over the weekend at RAF Fairford,” but called the police investigation “ongoing, complex and serious.” He said British officials had been speaking with U.S. counterparts throughout the week.

British officials have not publicly detailed the evidence behind the suspected Iranian link or said what the men may have been planning. Vicki Evans, the senior national coordinator for counter terrorism policing, said investigators were examining “multiple lines of inquiry” and “all possible angles — including possible foreign state involvement.”

Iran’s embassy in London said Monday that it “categorically rejects and strongly condemns” attempts to connect Iran to the incident. Foreign Minister Abbas Araghchi said British authorities were “barking up the wrong tree.”

U.S. President Donald Trump said the case “might be” linked to Iran, while Secretary of State Marco Rubio said it “clearly involved the hands of a foreign actor,” without naming a country, according to Al Jazeera. Israeli Prime Minister Benjamin Netanyahu said Israel had warned Britain about a potential “Iranian-sponsored attack,” Al Jazeera reported.

The five men’s release drew criticism from Trump and Rubio. Trump said British authorities “should not have done that” and asked, “How do you give bail to a terrorist?” Their release also prompted questions in Britain about whether police had overreacted, CBS News reported.

Laurence Taylor, the head of counter terrorism policing, called bail an “investigative decision” and said the men remain subject to “stringent conditions on their movement and contact with others.” He said investigators were examining whether the activity could have been carried out by people knowingly or unknowingly acting on behalf of a foreign state.

Police have not announced charges in connection with the incident. The investigation continues.