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, all UK nationals in their 20s, 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.
Laurence Taylor, head of Counter Terrorism Policing, said the police response on Sunday morning was due to “a range of information”, including a call from a member of public about “several vehicles acting suspiciously” close to the base.
He added that he hoped to close the “investigative scenes” by Wednesday.