Five men have been arrested and three vans are being examined by army bomb disposal experts in a possible foiled terror plot at RAF Fairford.
Gloucestershire Police said the first 999 call was received at around 12.45am today (Sunday), reporting three suspicious vehicles travelling towards the airbase.
Armed officers were deployed and five men were subsequently arrested on suspicion of offences under the Explosives Act. All five remain in police custody.
A photograph obtained by Wiltshire 999s from a local resident at around 8am shows five men surrounded by armed police near the scene.
The men appear topless in the image, while officers can be seen removing or examining their footwear. It is thought that officers were carrying out searches for potential devices or triggers.
Three large white vans – parked in the village of Whelford – are now being examined by the army’s specialist explosive ordnance disposal team near the US airbase.
A bomb disposal robot has also been deployed as specialists continue their examination of the vehicles.
A 400-metre cordon has been established around the vehicles, with around 85 households evacuated as a precaution.
Those forced to leave their homes have been offered refuge at a nearby leisure centre while the major incident continues.
The latest details were confirmed by Gloucestershire Police during a briefing to journalists near the scene this afternoon.
Police said they are working closely with Counter Terrorism Policing as enquiries into the incident continue.
Officers have asked members of the public not to speculate about the circumstances surrounding the incident. The force also thanked local residents for their “understanding and support”.
A huge emergency services presence remains in the area, with approximately ten Hazardous Area Response Team ambulances in attendance.
An estimated 100 police vehicles are also at the scene alongside numerous fire crews.
Police officers were seen going door-to-door evacuating homes in Horcott Road and nearby during the early hours of this morning.
A female police officer, speaking to the press at the scene at around 6am, described the situation as a “major incident”.
Roads surrounding RAF Fairford have been closed, with armed Ministry of Defence Police and Gloucestershire Police officers stationed around the perimeter.
A National Police Air Service helicopter was seen tightly circling RAF Fairford for around one hour during the early stages of the operation – and returned earlier.
The police chopper has remained cycling the area since around 9am – and was last seen in the skies above at 2pm.
Personnel from the Ministry of Defence Police, Gloucestershire Police, Wiltshire Police and Thames Valley Police have all been seen in the vicinity of the base.
RAF Fairford is operated by the US Air Force and is used to support American military operations, including deployments of strategic bombers.
Gloucestershire Police previously said it believed the incident was contained.
The force has not confirmed what, if anything, has been found inside the vehicles and has urged the public not to speculate while specialist examinations continue.
