British Prime Minister Andy Burnham said Monday a security incident at a U.S.-run military air base in England was "almost certainly" directed by Iran's Revolutionary Guard.

Burnham previously said there are strong indications Iran was linked to the apparent plan last month to attack the RAF Fairford air base, which has been used by American bombers to strike Iran in the ongoing war.

Police have arrested seven men in the investigation into the alleged plot, but all suspects have been released on bail and no one has been charged so far.