Five UK nationals in their 20s arrested near RAF Fairford in Gloucestershire were being released on police bail Monday, Counter Terrorism Policing said, while remaining under investigation for alleged terrorism-related offences. Police have not announced charges against any of the men.

Police were alerted early Sunday to three “suspicious vehicles” near the base, which has long hosted U.S. Air Force bombers. Homes were evacuated; a farmer who called 999 described hooded, masked men and vans blocking a lane in Whelford. The five men — aged 23 to 25, from Westminster, Camden, and Willesden — were first held on Explosives Act suspicions and further arrested on suspicion of preparing a terrorist act.

Assistant Commissioner Laurence Taylor said vehicles underwent extensive examination with military and forensic support, and that investigators were considering “every possible angle,” including whether proxies or people “knowingly or unknowingly” working for a foreign state were involved. The Iranian embassy in London “categorically” rejected media speculation linking Iran to the incident.

Prime Minister Andy Burnham chaired a Cobra meeting and urged the public not to speculate while facts are established. U.S. President Donald Trump, speaking at the Oval Office, said he was “surprised” the men were bailed and that “we would not have released them,” while saying the UK had worked closely with the United States. On Sunday, Trump had said the group had been under watch “for a long time,” according to Reuters; the Daily Mail (opens in new tab) reported that Whitehall sources insisted the arrests were not planned in advance.

Gloucestershire Police said evacuated households could return, though a cordon remained around the three vehicles. Airspace restrictions within about five miles of the base stayed in force.