Trump also indicated U.S. officials were cooperating with their British counterparts on the case.

“Look, they’ve been very good. They are working with us very closely,” he said, adding that the United States knew “everything” about the suspects.

Separately, Secretary of State Marco Rubio said the incident “clearly involves the hands of a foreign actor” — an allegation British officials have not confirmed.

The five men, all British nationals in their 20s from London, were arrested Sunday on suspicion of terrorism and explosives offenses after three vehicles were seen moving toward RAF Fairford, a British air force station about 90 minutes west of London.

Counterterrorism police took over the case after a major incident was declared, disrupting life in the normally quiet, rural community of the Cotswolds.

On Sunday, counterterrorism police said the men had been arrested on suspicion of committing offenses under the Explosives Act, a British legislation dating back to 1875 that regulates manufacturing, keeping, selling, carrying and importing of gunpowder and explosive substances. The men were further arrested on suspicion of preparation of a terrorist act.

“What seems to be happening is that you’ve got a developing investigation where the custody clock for the terrorism arrest, which is a very long custody clock, has stopped,” said Max Hill, a former Director of Public Prosecutions of England and Wales.

In the U.K., police can usually hold someone for up to 24 hours before they have to charge or release them although officers can apply to extend that time if they suspect a serious crime has been committed. Suspects arrested under the Terrorism Act can be held without charge for up to 14 days.

“So there must be an element of uncertainty about whether ultimately any terrorism-related charges are going to emerge,” Hill told NBC News in a telephone interview Tuesday. Releasing the suspects on bail also doesn’t mean that they won’t be taken back into custody, he added. “But it does indicate that there’s just not enough for a formal remand application.”

The incident prompted questions about whether a foreign actor could be involved — in particular, Iran, after the country’s Islamic Revolutionary Guard Corps warned Britain this summer that RAF Fairford could be a “legitimate target.” It came months after then-Prime Minister Keir Starmer gave permission for the U.S. to use its bases for “specific and limited defensive” operations against Iran.

The Iranian Embassy in Britain denied any involvement Monday.

During an appearance on Fox News later Monday, Rubio said that “what happened, what almost happened, what could have happened in the U.K. over the weekend, is a very serious situation.”

“There’s a lot more news that’ll come out on this in the days to come,” he added.

Taylor, noted that “it was simply not possible for me to go into detail about every strand that we are looking at and all of the intelligence we have got,” something he said was not unusual for this type of investigation.

“It is unusual for it to be as visible as it is in this incident,” he said, adding that his team was working with international partners on the investigation.