A quantity of petrol but no explosive devices were found in the vans that sparked a major security alert near an RAF base used by the US, police have said.

Five men who were arrested on suspicion of explosives offences and later terrorism were all released on bail on Monday, which head of UK counter-terrorism Policing Assistant Commissioner Laurence Taylor said was an investigative decision.

Villagers living near RAF Fairford in Gloucestershire, dozens of whom were dramatically evacuated from their homes on Sunday morning, were slowly returning to normal on Tuesday.

Giving an update on Tuesday, Mr Taylor said: “We can confirm that no improvised explosive devices were found. However, a quantity of petrol was recovered.

“Yesterday we released the five men on police bail. They remain under investigation and must adhere to strict conditions while we continue our work.

“The safety of the public is at the forefront of our investigative decision making, and this was certainly the case yesterday.

“I understand why this development will have come as a surprise to many, but I’d like to reiterate that it was investigative decision, and one which is grounded in experience and careful consideration of policing powers.”

Police cordons near the base are expected to be completely lifted on Wednesday, and searches of the London homes of the five suspects are complete.

Mr Taylor said the incident has been worrying for lots of people, adding that this is “heightened by the international commentary that we are seeing”.

Speculation over whether Iran had any involvement in the drama, including by tasking proxies to carry out crimes on their behalf on UK soil, remains rife.

US secretary of state Marco Rubio claimed in a television interview that the suspected plot “clearly involves the hand of a foreign actor”, but refused to provide further details.

Potential involvement by Iran was understood to be one line of inquiry for British investigators, and the nation has used proxies in the past to carry out acts in the UK.

But its London embassy fiercely denied any involvement in the events in Gloucestershire.

Speaking to Fox News, Mr Rubio said: “It’s one that clearly involves the hand of a foreign actor. I won’t get into great detail about that yet.

“I do want to thank the authorities in the United Kingdom who have been very co-operative and on top of it.”

He added: “I know a lot of people are disturbed by the news that some of these people have been released on bail, as some of the people are being investigated, and obviously we’re engaging with them on all of that.

“Beyond that, I would argue that they’ve been very co-operative and very helpful on something that’s a very serious incident.”

The five suspects, all UK nationals, are a 24-year-old from Camden, north London; and a 23-year-old, two 24-year-olds, and a 25-year-old all from Westminster, central London.

Police would not confirm when they are due to answer bail.