British-Iranian Man, 27, Arrested Over Suspected Terror Plot Targeting U.S.-Run RAF Fairford

British counterterrorism police arrested a 27-year-old dual U.K.-Iranian national in London on Thursday on suspicion of preparing terrorist acts, in an investigation into suspicious activity at RAF Fairford, the English air base used by U.S. bombers.

The man was arrested in the City of Westminster. Police also interviewed a 26-year-old British national under caution. Detectives have not said how either man is connected to the events at the base.

The arrests are the latest step in an inquiry that began last weekend. Police were called to look into suspicious activity outside RAF Fairford late Saturday night into early Sunday morning. In the early hours of Sunday, five British men in their 20s, all from London, were arrested near the base on suspicion of explosives and terror offenses. Officers found gasoline in three vans linked to the five suspects, but no explosives. All five were later released on bail.

Prime Minister Andy Burnham has said there are "strong indications that Iran played a part" in the incident. Iran has denied any involvement. According to officials, "our specialist teams are interrogating multiple lines of inquiry," including the possibility of foreign state involvement.

RAF Fairford sits about 100 miles west of London in Gloucestershire. It has hosted American bombers used in operations in the Middle East, including recent operations connected to the war with Iran, which makes it an obvious target at a time of heightened tension.

The decision to release the five original suspects on bail has drawn criticism from U.S. officials. Top American officials questioned the move, and President Donald Trump said he would have handled it differently. British police have not publicly explained the bail decision beyond the usual rules that apply when investigators do not yet have enough evidence to charge.

The case is a delicate one for Burnham's government. Britain has stood alongside Washington on the Iran war while trying to avoid direct involvement, and an accusation that Tehran backed a plot on British soil would raise the pressure to move closer to the American position. At the same time, officials know that naming a state sponsor before the evidence is nailed down could damage the investigation and any later prosecution.

Counterterrorism officers took over the Fairford inquiry from local police shortly after the first arrests. Under British law, suspects held on terrorism offenses can be detained for questioning for up to 14 days before they must be charged or released.

The investigation continues, and police have asked anyone with information about the activity near the base to come forward.