A dual Iranian-British national has been arrested in relation to the incident at RAF Fairford last week.
The 27-year-old man was on suspicion of the preparation of terrorist acts, Counter Terror Police confirmed on Thursday.
A second man, a 26-year-old British national, was also questioned, while searches have been carried out at two properties in Westminster.
Senior National Coordinator for Counter Terrorism Policing Vicki Evans said: “The investigation into circumstances surrounding events in Gloucestershire is hugely complex, and our specialist teams are interrogating multiple lines of enquiry.
“As we’ve made clear, we’re looking at all possible angles – including possible foreign state involvement. I’d like to thank the public for their continued support and patience whilst we work through this investigation.”
It comes after five men, all British nationals in their 20s, were arrested near the RAF base, which is also used by the United States in Gloucestershire on Sunday on suspicion of explosives and terrorism offences.
All five have since been bailed pending further investigation.
Earlier this week, US Secretary of State Marco Rubio suggested “a foreign actor” may have had involvement in the incident.
And, Prime Minister Andy Burnham told the BBC’s Chris Mason on Wednesday: “There are strong indications that Iran played a part in what happened over the weekend at RAF Fairford, but of course it remains an ongoing, complex, and serious police investigation.
“And of course, we are working closely with our colleagues in the United States of America.
“Police in Gloucestershire, our counter-terrorism police have done an outstanding job. I thank them for that. We will say more in due course, but we can confirm our belief that we believe Iran to have played a part.”
Pressed by Mason on what led the government to believe Iranian involvement, Burnham replied that he “can't go into all of those details, but obviously I wouldn't say it lightly”.
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