The Air Force has withdrawn B-1 and B-52 bombers from RAF Fairford in England following a security investigation into an alleged terror plot targeting the U.S.-operated air base.

The bombers were moved back to their home bases in the United States, according to a Pentagon official who spoke Sunday on condition of anonymity because the military movements are sensitive.

RAF Fairford had become a major staging point for American bomber operations during the war with Iran, with aviation trackers observing B-1 and B-52 aircraft operating from the base since the conflict began. Several B-1 bombers were seen departing the facility Sunday.

The withdrawal comes as President Donald Trump continues to weigh his next steps in the conflict with Iran, including the possibility of additional U.S. strikes.

“We have decisions that I'll make about Iran. Iran's been decimated. So the only question is, it’ll either be the easy way or the hard way,” Trump told reporters Saturday.

The security concerns at Fairford emerged after British authorities arrested a dual British-Iranian national in central London last week on suspicion of plotting a terror attack. The arrest followed a security incident at the air base in late September.

Six people in total have been detained and released on bail as part of the investigation. British authorities have linked the suspected plot to Tehran, although Iran has denied involvement.

Located roughly 100 miles west of London, RAF Fairford has hosted U.S. bombers for decades and has served as an important base for American military operations in the Middle East.

The Pentagon is also moving additional naval forces toward the region. The USS Theodore Roosevelt aircraft carrier and the USS Makin Island amphibious readiness group, which carries thousands of sailors and Marines, are heading toward the Middle East.

The deployments could bring the number of U.S. aircraft carriers operating in the region to three by the end of October as Washington weighs its options in the conflict.