British authorities confirmed that five suspects were arrested near RAF Fairford in Gloucestershire, southwest England. They are accused of planning a terrorist act; police initially detained them on suspicion of offences under explosives legislation.

A 400-metre exclusion zone was set up around three suspicious vans, while the military carried out checks. About 85 homes were evacuated as a precaution. British media reported suspicions that the vans may have contained explosives and chemicals, but their contents and any danger have not been confirmed and remain under examination.

The Guardian reported that police seized materials and are assessing their risk and whether they could technically have been used in an attack. Media reports said the arrests were not part of a pre-planned operation based on intelligence. Authorities are examining several possibilities, including whether Iran or another state may have instigated a plot, but no state involvement has been established publicly.

Security at the base was increased after the arrests, with roadblocks, armed officers, ambulances and fire engines deployed. Home Secretary Shabana Mahmood described the incident as serious and said the situation was under control. A government spokesperson said officials would not comment further while the investigation was under way.

RAF Fairford is used by the US Air Force as a forward operating base and hosts heavy bombers including the B-1B, B-2A and B-52H. Britain permitted the United States to use the base for what London called defensive strikes against Iran in early March, after US and Israeli attacks began on February 28. In July, Iran’s Islamic Revolutionary Guard Corps described British bases used by the US for attacks on Iran as “legitimate targets.” Those statements do not establish a link to the current arrests.

The base has been associated with US strategic air operations since the Cold War and was used during the 1991 Gulf War and the 2003 Iraq War. The current investigation is ongoing, and British authorities have released few further details.