The announcement that the five British suspects had been released on bail came from the London Metropolitan Police, which added that the investigation is continuing.
"I can confirm - following extensive questioning and investigation - that the five people who were arrested have been released on bail," said Assistant Commissioner Laurence Taylor of the Metropolitan Police's counter-terrorism unit. He added that he understood the incident had geopolitical implications and said investigations were continuing.
The five are men, between 23 and 25 years old, living in London.
Explosives are questioned
Several media outlets, including the British Daily Mail, reported on Monday evening that samples of material found in the arrested men's vans were not usable explosives. After the arrest, there were reports that police had found explosives.
British Prime Minister Andy Burnham called an emergency meeting due to developments around Fairford Air Base, where both British and American forces operate.
On Monday, Iran consistently denied, through its London embassy, all claims that the country was involved in the incident.
Tips from the public
The tip that led to the operation came from a local farmer who called the police.
When they saw me, they ran - some into the field and others towards the neighboring village, she tells the BBC .
US President Donald Trump chose to quickly comment on Sunday's arrests - and claimed that security services had the people under surveillance.
Trump's statement was soon questioned by independent security analysts in the UK, who said the arrests came after a tip from the public.
On Monday, President Trump was again asked about the incident. He nodded in the affirmative when asked by reporters if there was an Iran connection.
You will hear all about it soon. We took them, he replied.
