US President Donald Trump has said five men arrested near RAF Fairford in England were looking to do “big damage” and had been under investigation by American and British authorities.

The men, aged 23 to 25 and described by police as British nationals from the London area, were arrested by armed officers in the early hours of Sunday after a tip-off that three vans were heading toward the base. They were later released on bail under stringent conditions on Monday and remain under investigation, uncharged.

RAF Fairford is a forward operating location for US long-range bombers, and American B-1 bombers have flown strike missions against Iran from it since March, reports say. Trump called the arrests “fantastic” and praised joint cooperation with Britain.

British police have not publicly confirmed what the vans contained, though controlled detonations were reported at the scene. Reports said investigators were examining several possible motives, including an Iranian-linked plot; Iran has denied any role.