British police found no explosives but a quantity of petrol in three vans linked to five suspects arrested near a US-operated air force base in England. The surprise decision to release the men on bail has raised questions on both sides of the Atlantic.

The five young British men, all in their twenties, were arrested early Sunday near RAF Fairford on suspicion of explosives and terrorism offences. They were freed on Monday. The base has hosted American bombers for decades, including during this year’s war with Iran.

Laurence Taylor, head of UK Counter Terrorism Policing, said the bail decision was grounded in “experience and strategy”. He stressed the suspects face strict conditions and remain under investigation. About 85 homes near the base were evacuated during the security operation.

US President Donald Trump said he was surprised. “I wouldn’t have done that,” he told reporters. Secretary of State Marco Rubio said the case “clearly involves the hands of a foreign actor” but did not name a country.

Police are pursuing “multiple lines of inquiry”, including whether the suspects had a link to Iran. Iran has denied any involvement.