(LONDON) -- A police cordon remained in place on Monday near a major air base hosting U.S. forces in the southwest of England, where British police arrested five men early on Sunday on suspicion of terrorism and explosives offenses.
The men were detained in possession of three vans close to RAF Fairford, which has long served as a key European hub for the U.S. Air Force and a vital staging point for long-range operations in the Middle East -- including in the ongoing conflict with Iran.
Counter Terrorism Policing said on Monday that all five men arrested were from London, all were British nationals and all were aged between 23 and 25. They were detained "on suspicion of offences under the Explosives Act and preparation of a terrorist act contrary to Section 5 of the Terrorism Act," CTP said.
Police said they are still working to "establish the full circumstances of the activity of those arrested, their knowledge and any motivation behind this incident."
Speaking to BBC Radio 4 on Monday morning, British Defense Secretary Wes Streeting said he would not "comment in detail on operational security matters. Because, often, the more we might say the more insight we give to those who would wish us harm, and do us harm given the opportunity."
Streeting said the investigation was "well under way" and thanked those involved in the arrests, the evacuation of the town and the investigation. Police said that at least 85 homes were evacuated during their response on Sunday.
Streeting thanked an anonymous farmer -- who also spoke with the BBC -- who said she called in the threat after coming across the "hooded and masked" men and vans in the early hours of Sunday morning in the village of Whelford, close to RAF Fairford.
Streeting thanked the tipster for calling in the threat, though said the caller only "had a partial picture" of the situation. "I won't go beyond that, in terms of commenting on operational security matters," Streeting added.
The farmer told the BBC she believed authorities had "dropped the ball" in allowing the suspected attackers to get so close to the base.
Public frustration at the incomplete picture, Streeting continued, is "a small price to pay" to protect operational security. Streeting also refused to comment on the identities, aims or motivations of the five detained men.
Streeting declined to give further details on what police and intelligence authorities may have known about the alleged plot, though welcomed President Donald Trump's praise of an operation that he said had been ongoing for a "long time."
Trump told reporters on Sunday that the suspects were "looking to do big damage" to U.S. forces present at RAF Fairford. "The arrest in the U.K. was fantastic. Working with Britain, it was an amazing job," Trump said.
The U.S. military has used RAF Fairford intensively amid the ongoing war with Iran -- though so far no connection to Iran has been confirmed or established by authorities. The base has been used by American B-52 and B-1 heavy bombers operating in the Middle East.
When asked of potential Iranian involvement in the suspected plot, Streeting said he was not "drawing a connection with Iran," before adding, "We know that Iran and their proxies wish to do us harm."
The Iranian embassy in London denied any involvement in the incident, posting to X to condemn what it called "recent unfounded and malicious speculations published by some British individuals and media outlets."
"The circulation of such fabricated speculations, particularly in the aftermath of the criminal acts of aggression committed by the United States and the Israeli regime against the Iranian people, will serve no purpose other than to fuel Iranophobia propaganda in the UK," the embassy said.
"The Islamic Republic of Iran reserves the right to take appropriate legal measures, as necessary, to safeguard the rights and interests of the country and its people in response to misleading and damaging media narratives," it added.
ABC News' Victoria Beaule contributed to this report.