British counterterrorism police have released five men on bail as they continue investigating an alleged plot targeting RAF Fairford, the UK air base used by US bombers. The men, aged 23 to 25, were arrested near the base on suspicion of offences under the Explosives Act and preparing a terrorist act.

People familiar with the investigation said the vans used by the men contained no viable explosives. Laurence Taylor, the UK’s head of counterterrorism policing, said the suspects remained under investigation. Police are keeping an open mind about possible links to geopolitical events, including individuals working for a foreign state.

Security officials suspect US B-1 bombers were a likely target. Iran’s Embassy in the UK categorically rejected attempts to link Iran to the arrests. About 85 nearby households were evacuated before residents were allowed home on Monday evening.

The probe continues as US and UK officials discuss possible foreign involvement. Further updates are expected as the investigation develops.