FAIRFORD, United Kingdom (AFP) — British counter-terror police were probing whether Tehran was involved in a potential bomb threat near an air base used by the United States military in its war against Iran, UK media reported Monday.

Police were called to the Royal Air Force Fairford air base in southwestern England in the early hours of Sunday, after they were alerted to “suspicious vehicles” in the area.

Authorities have not officially confirmed details about the nature or origin of the threat, but have arrested five men on suspicion of “preparing a terrorist act” and on explosives charges, who remain in custody, and bomb disposal experts were seen at work at the site.

US President Donald Trump overnight said “we know all about them” when asked about the suspects, appearing to nod when asked if there was a connection to Iran.

“You’ll be hearing about it very soon. We caught them,” said Trump, without giving more details.

Earlier Sunday he said the suspects were “looking to do big damage” at the base, where US bombers are stationed, without providing additional details.

The adjoining village of Whelford, where the men were arrested, was evacuated on Sunday and remained cordoned off on Monday morning, as residents spent the night in alternative accommodation.

Gates to the Fairford air base were blocked off by heavy construction vehicles, Agence France-Presse reporters saw, as UK defense minister Wes Streeting said the investigation on the site “continues today.”