The British government believes Iran "played a part" in an incident last weekend at the RAF Fairford base.

"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," United Kingdom Prime Minister Andy Burnham told the BBC. 

Tehran has denied any involvement in the incident at the base, which the U.S. has used to launch aircraft that carry out strikes on Iran. 

British police on Sunday said that five men had been arrested "on suspicion of offenses under the explosives act" in connection with the incident. The U.K. released the suspects on bail shortly after their arrest.

Reports by local media, which authorities haven't confirmed, suggested the men were fuel thieves trying to steal diesel from farms in the area or possibly from the base itself, but Burnham indicated Wednesday that a more serious plot was being undertaken, ABC News reported.