US Secretary of State Marco Rubio says the weekend incident at RAF Fairford "clearly involves the hands of a foreign actor"
Speaking to US media, he doesn't give further details but thanks UK authorities for being "co-operative" and "helpful"
Five men arrested on suspicion of terror offences near the base, which is used by the US military, were released on bail on Monday - here's what else we know
The men - all UK nationals in their 20s who live in London - had been arrested under the Explosives Act and on suspicion of preparing a terrorist act
AC Laurence Taylor, the head of UK counter terrorism policing, has said officers are pursuing multiple lines of inquiry, including if proxies working on behalf of a foreign state could've been involved - the Iranian embassy in the UK denies involvement
Residents from 85 households evacuated on Sunday have started returning home. With a cordon still in place and roads blocked, they want to know how long the disruption will last, writes our reporter
Image source, ReutersAssistant Chief Constable Richard Ocone says that work to establish the full nature of the incident is ongoing.
He says the force is working closely with its partners in counter-terrorism policing.
He adds that a 400m cordon is in place around the vehicles while examinations take place.
Eighty-five households have been advised to evacuate with a leisure centre open to house those unable to stay with family or friends.
Assistant Chief Constable Richard Ocone now says five men were arrested on suspicion of committing offenses under the Explosives Act.
They were taken into custody where they remain, he says.
Image source, ReutersWe've just heard from Gloucestershire police assistant chief constable Richard Ocone, who says the force received a call at about 00:45 BST on Sunday morning relating to "three suspicious vehicles" travelling toward RAF Fairford.
A woman who has lived near RAF Fairford for the last 50 years says there has been an increase in military security in recent weeks.
She told the Press Association that "very heavy vehicles" had been put across all gates, with "great big concrete walls” also placed behind some gates, including on Dunfield Loop and Whelford Road.
Image source, Getty ImagesPolice have been responding to the major incident since the early hours of this morning, with nearby Fairford Youth Football Club, on Horcott Road, impacted.
Posting on its Facebook page, the club said today's games had been postponed "due to circumstances beyond its control".
The post said: "Please don't head to the club."
Image source, Getty Images/Justin Tallis
Image source, Getty Images/Justin Tallis
Image source, Getty Images/Leon NealOne resident who has lived in the area for 18 years said she was woken by police banging on her door.
She was then ordered to leave straight away, without being able to take her dog with her.
Jo says she knew it "must be serious" after she was evacuated from her home at about 07:00 BST.
"We were asleep and they were just banging on our door.
“They said it was a critical incident and we’ve got to leave straight away, and they basically wouldn’t leave the doorstep until we left.
“We just had to throw our clothes on and come. We didn’t know anything.”
Jo says the police waited at the door until they left.
“I didn’t even brush my teeth or nothing."
Jo says she had to leave her dog, Coco, after the rush.
“They just implied that we shouldn’t take him. We fed him, but it’s not about that, is it, it’s just he’s on his own for hours.”
The police news conference on the RAF Fairfield incident, which was due to start at 12:45 BST, has evidently been delayed.
Our reporters are waiting for a spokesperson for either Gloucestershire or counter-terror police to arrive. We will update you when we hear more.
Jonathan Beale
Defence correspondent
A British Army bomb disposal team – known as an Explosive Ordnance Disposal team – is still carrying out operations, according to a defence source.
Pictures from a news helicopter show a remote controlled robotic system being used to inspect a number of stationary white vans in the area.
A defence source said UK Military Police were also supporting their civilian counterparts in providing a security cordon around the area.
Leigh Boobyer
Live page reporter
While we wait for police to give an update on the major incident - here are how things look on the ground.
Image source, PA MediaArmed police are placed on roads around RAF Fairford while investigations continue
Image source, ReutersSome residents in the village have been evacuated to a leisure centre and have not been told when they can leave
Image source, ReutersEmergency services have been positioned in and around the village since the early hours
Image source, PA MediaCounter-terrorism police are leading the investigation
Image source, PA MediaGloucestershire Police say several men had been arrested on suspicion of offences under the Explosives Act.
Police cordon expands to RAF Fairford amid major incident
While we wait for police to give us their update, the cordon, which has been in place since the early hours of this morning, has been expanded to include RAF Fairford.
Our reporter Alastair McKee says everyone has been moved out of the vicinity of the air base and into the village further down the road.
We're expecting to hear an update from authorities shortly.
You'll be able to watch live at the top of the stream when the conference gets under way.
We'll bring you all the key news lines here, too.
Image source, ReutersThere are multiple emergency service vehicles in the Gloucestershire village
A Whelford resident has described the moment he saw police apprehend the suspects.
Jeff told the BBC that he heard "shouting outside his front door", although he couldn't be sure where it came from.
He says he then looked out of his window and saw "people being held by police outside".
The moment was "a bit surreal", he says, but adds that "you get used to funny things going on sometimes around the base [RAF Fairford]".
Helicopter footage taken near RAF Fairford has shown a wheeled robot operating near three parked white vans.
Earlier, Gloucestershire police said the Army's specialist explosive ordnance disposal team is examining a number of vehicles in the village of Whelford.
The force has not confirmed which vehicles were being examined, or mentioned the use of a robot.
A resident evacuated from his home near RAF Fairford in the early hours of Sunday says three "unusual vans" appeared in the area overnight.
Julian Tudsbery claims footage recorded by doorbell cameras in the area since the evacuations has shown "some robots looking in the back of these vans".
He says: "There were these three vans that arrived in the middle of the village and a resident reported them to the police straight away."
Police have not made any mention of vans or the use of robots.
Annabelle Martin
Reporter
Jason, an evacuated resident who has been at the leisure centre since about 7am, told the BBC that he was first made aware of the incident after seeing "some messages on the village group" last night.
Jason says he heard the helicopter but went to bed as normal before being woken by police officers.
"It all happened very quickly. We just packed our stuff up and came here."
He says the police described the situation as a "major incident" and had given residents "basic updates".
Jason says he had to bring his ill cat with him, that was supposed to be heading to the vets today.
He says: "It's been a bit full on. A bit eventful."
We're now seeing live aerial pictures from near RAF Fairford in Gloucestershire where there is a heavy police presence following the arrest of several men on suspicion of offences under the Explosives Act.
You can watch live at the top of the page.
Image source, Getty ImagesHome Secretary Shabana Mahmood says emergency crews responding to the incident near RAF Fairfod believe it is now "contained".
"I would like to thank the emergency services for their swift response to the major incident in Gloucestershire this morning and their reassurance that they believe the incident is contained," she writes on X.
"Whilst investigations are ongoing it would be inappropriate to comment further."
Sammy Jenkins
BBC News, Live page reporter
Image source, REUTERS/Toby ShepheardLocated on the border of Gloucestershire and Wiltshire, RAF Fairford has long been used as a forward operating location by the US Air Force (USAF).
Its history with the US Air Force goes back decades, with the site occupied by USAF Strategic Air Command during the Cold War and later the first Gulf War in 1991.
B-52 bombers were also deployed by USAF from the site on raids to Iraq in 2003.
It was most recently used on 1 March though after former prime minister Sir Keir Starmer granted permission for "defensive" US action against Iranian missile sites from the base.
US heavy bombers soon started taking off from RAF Fairford in what the Ministry of Defence (MOD) described as "defensive missions to destroy Iran's missile capabilities".
The move came after after the US and Israel began attacking Iran on Saturday 28 February.
Chris Partridge
BBC News weapons analyst
Image source, Getty ImagesRAF Fairford saw large amounts of activity earlier this year as US Air Force heavy bombers departed to strike targets in Iran.
I saw B-52 bombers from the Cold War era departing from the airbase loaded up with AGM-158 air launched cruise missiles for stand-off precision attacks.
These weapons have a range of some 500 miles, giving US military planners the ability to strike high-value, protected targets at distance.
In additional I also saw newer B-1b bombers loaded up with GBU-31(v) 3/b JDAM free-fall precision guided bombs - these types the penetrating "bunker busting" variety. The bombs would likely have been selectively used against hardened targets or underground weapons' stores.
Each bombing mission, depending on the location of the target, would likely have taken about 12 to 15 hours in total there and back, with air-to-air refuelling both ways.
The bombers would also have been supported by fighter jets closer to the theatre - such as F/A-18 Super Hornets and F-16 Vipers.
These jets would carry out Suppression/Destruction of Enemy Air Defences (SEAD/DEAD) roles to guard against surface to air missile threats and radar-guided anti-aircraft fire from the ground.