The public is slowly getting more information about what happened near the RAF Fairford airbase at the weekend – but many questions remain unanswered.

We know that two early-morning calls were made to police about suspicious vehicles, and that five men, all British nationals in their 20s, were arrested on suspicion of explosives offences and terrorism offences.

We also know they were later released on bail, and the BBC understands that one of the men was the first 999 caller. Prime Minister Andy Burnham has now said the UK government believes Iran “played a part” in the incident.

Here is what we know about how the incident unfolded, and what has happened in the days since.

We now know that in the days leading up to the incident, security was increased around RAF Fairford, one of the UK’s most important military sites, which is used by the US Air Force.

There were also reports of heightened police activity around the base on Saturday evening, hours before three suspicious vehicles were reported to police.

Gloucestershire police say they received a call just after midnight on Sunday 27 September about “three suspicious vehicles” that appeared to be travelling towards RAF Fairford.

The BBC now understands that one of the five men who was later arrested and then bailed had made the call himself.

Nearly an hour later, a farmer living close to the base called 999 after seeing three vans parked in a “weird formation”.

There was “a large group of hooded and masked men” near the vans who started to “panic” when they saw her, she told Radio 4’s Today programme.

The woman, who has remained anonymous, said she initially tried to contact the Ministry of Defence police at RAF Fairford, but no one picked up, so she dialled 999.

“Within 10 minutes the village was full of armed police,” she said.

Shortly afterwards – although the exact time is unknown – Gloucestershire Constabulary arrested five men in the Whelford area, a village right next to the base.

They were arrested on suspicion of committing offences under the Explosives Act.

A grainy image purporting to show the moment of arrest shows five men sitting on the ground, shirtless and in handcuffs under guard by police officers.

The BBC has been unable to verify the original source, but BBC Verify has geolocated the image and confirmed it appeared to be authentic.

After sunrise, police declared a major incident in Whelford, external and set up a 400m (1,312ft) cordon around the three vehicles.

The Army’s Explosive Ordnance Disposal unit was brought in to examine them, and aerial pictures showed a remote-controlled robot approaching some white vans.

About 85 households in Whelford were evacuated to a local leisure centre.

Some residents said they had been “shaken by the incident” but that “community spirit and local support has been exceptional”.

By Sunday afternoon, Counter Terrorism Policing had confirmed it was leading the investigation.

In a statement, it said the five men had been further arrested on suspicion of preparing a terrorist act.

The investigation was still in its early stages, Deputy Assistant Commissioner Vicki Evans said, and the public was asked “to follow official channels for updates” and not to speculate.

At about 16:00 BST, US President Donald Trump told reporters the arrest of the five suspects was “fantastic” and “an amazing job”.

“We had them under investigation. They were looking to ‌do big ⁠damage to our fort and working with the British worked out great… We had them under view for a long time, and we got them.”

The US is connected to this incident because its air force operates RAF Fairford, and has used the base to carry out strikes against Iran.

At about noon on Monday, counter-terror police released more information on the five men, external who had been arrested – they were all from London and aged between 23-25.

In a statement, Counter Terrorism Policing said they were being held under the Police and Criminal Evidence Act (PACE) and that a custody extension has been secured.

A cordon remained in place in Whelford.

Within hours, however, counter-terror police announced that all five men would be released on police bail after “extensive interviews and enquiries”.

Assistant Commissioner Laurence Taylor stressed that the men were subject to “stringent conditions on their movement and contact with others.”

“They absolutely remain under investigation as we explore multiple lines of enquiry,” Assistant Commissioner Laurence Taylor said.

Speaking from the White House, Trump questioned the decision, saying he was “surprised that they released them”, adding: “I wouldn’t have done that.”

Also on Monday afternoon, the prime minister chaired a Cobra meeting and urged people “not to speculate while the authorities establish the full facts”.

Taylor defends the decision, saying it was “grounded in experience and careful consideration of policing powers”.

Later on Monday, US Secretary of State Marco Rubio told Fox News that the incident “clearly involves the hands of a foreign actor”, but did not provide evidence or further details.

Counter-terror police gave another update on Tuesday evening, saying properties in London had been searched as part of the investigation. No further details were given.

The three vehicles had also undergone an “extensive examination” with the support of military and forensic experts, Assistant Commissioner Taylor said.

The Counter Terrorism Policing boss said that no improvised explosive devices were found in the vans, but a “quantity of petrol” was recovered.

Three days on, the BBC has learned that one of the men who had been arrested had made the first 999 call.

It remains unclear why the man called police, or what he told them.

Also on Wednesday, Gloucestershire Police removed the cordon and reopened the scene.

A few hours later, Prime Minister Andy Burnham told the BBC that there were “strong indications that Iran played a part” in the incident.

“We will say more in due course but we can confirm… that we believe Iran to have played a part,” he said, without providing further details.

Tehran has strongly denied any involvement.