Then men, all from London and aged in their 20s, were held on suspicion of explosive offences and preparation of a terrorist act.
The suspects arrested over a potential terror plot near an RAF base used by the US are all British nationals aged in their 20s and from London, police have said.
The men were were arrested in Whelford, Gloucestershire in the early hours of Sunday, initially on suspicion of explosives offences and later terrorism.
A villager in Whelford dialled 999 after she saw three vans and a group of masked men near the base, and dozens of homes had to be evacuated as bomb disposal teams were called in.
Counter-terrorism police are understood to be investigating if any potential plot could be linked to Iran, which has used proxies to carry out crimes on British soil in the past.
