Five British men were arrested on Sunday, 27 September, on suspicion of offences under the Explosives Act and preparation of a terrorist act, after police were alerted to three suspicious vehicles near the airbase. No improvised explosive devices were found in the vehicles, but investigators recovered a quantity of petrol.

On Thursday, Counter Terrorism Policing arrested a 25-year-old British-Iranian man for the same offense as part of investigations. All six men were later released on bail.

On Sunday, the Pentagon confirmed that the U.S. had withdrawn all B-1 bombers from the airbase. The following day, U.S. President Donald Trump told reporters that the United States had known of a “threat” which led them to move the bombers.

Counter-terror police — supported by the MI5 intelligence service — are currently investigating “possible foreign state involvement” as part of their enquiries.

U.K. Prime Minister Andy Burnham has said the government believes “Iran to have played a part” in the incident.