A quantity of petrol but no explosive devices were found during searches of the three vans near RAF Fairford in the west of England, counter-terror police have said.
Five men were arrested on suspicion of explosives offences and later terrorism offences after the vehicles were spotted in the early hours of Sunday, sparking a major security incident around the base which is operated by the US military.
They were released on bail the following day in what police described as an “investigative decision” which was “grounded in experience and strategy”.
It comes after US Secretary of State Marco Rubio said it was clear a “foreign actor” had been involved, without providing evidence.
Police were alerted to “three suspicious vehicles” in Whelford, a village which lies directly east of the base, by a member of the public in the early hours of Sunday morning.
The woman who called 999 told the BBC it was “pure luck” she had spotted them, having arrived home to find the road blocked and a “large group of hooded and masked men”.
“I believe that my 999 call foiled whatever plans they had,” she said.
A bomb disposal team arrived on scene shortly afterwards and a 400m (1,312ft) cordon was put in place.
But Laurence Taylor, head of Counter Terrorism Policing, told reporters on Tuesday that the police response that morning was due to “a range of information”.
Police cordons near the base are expected to be completely lifted on Wednesday, while residents from the 85 homes evacuated on Sunday have been allowed to return to their properties.
The five men are all UK nationals aged between 23 and 25. Four of them live in Westminster and one in Camden, and searches of their homes are now complete.
Assistant Commissioner Taylor previously said their bail was “subject to stringent conditions on their movement and contact with others” as they remained under investigation.
“The safety of the public is at the forefront of our investigative decision-making, and this was certainly the case yesterday,” he said on Tuesday.
“I understand why this development was surprising to some, but I would like to reiterate that this is an investigative decision and one which is grounded in experience and strategy.”
It comes a day after US President Donald Trump said he would not have let the five men out on bail and that he was “surprised” they had been released.
