Tests on the materials found in the three vans stopped near RAF Fairford showed they were not viable explosives, according to Counter Terrorism Policing, and the five men arrested over the suspected plot were released on police bail without charge. Assistant Commissioner Laurence Taylor said the men remain under investigation and face strict conditions on their movements and contact with others. Police expect to reduce the cordon around the village of Whelford and allow evacuated residents to return home.

The men, all British nationals from London aged 23 to 25, were arrested within 25 minutes of a 12:45 a.m. call on Sunday from a farmer who reported three suspicious vans heading toward the base, which hosts US B-1 and B-52 bomber operations against Iran. They were first held under the Explosives Act, then further arrested on suspicion of preparing a terrorist act. Army bomb disposal teams examined the vans inside a 400 meter cordon and about 85 households were advised to evacuate. The farmer has told the BBC she is "100% certain" she saw 8 to 10 men, not only the five arrested.

A source familiar with the investigation told Reuters an Iran-linked motive is considered the most likely, while Russian sabotage and an Islamist plot are also being examined. Taylor said police are investigating every possibility, including that the men acted as proxies, knowingly or unknowingly, on behalf of a foreign state. Iran's embassy in London said it "categorically rejects and strongly condemns" speculation linking Tehran to the arrests and reserved the right to take legal measures over what it called misleading media narratives.