WASHINGTON (AP) — The U.S. Air Force has brought home its bombers stationed at a U.S.-run military air base in England used to strike Iran following an investigation into a planned terror attack at the RAF Fairford base.

The bombers were redeployed back to their home bases in the United States, according to a Pentagon official who was not authorized to discuss sensitive military movements and spoke Sunday on condition of anonymity.

Aviation watchers such as the Military Air Tracking Alliance have observed dozens of B-52 and B-1 bombers operating out of RAF Fairford since the opening days of the Iran war. Observers noticed a host of B-1 bombers fly out of the base on Sunday.

A dual British-Iranian national was arrested in central London last week on suspicion of plotting a terror attack, following a security incident at RAF Fairford in late September. In total, six people have been taken into custody and then released on bail during the investigation.

British authorities have linked the incident to Tehran. Iran has denied involvement.

RAF Fairford, located 100 miles (160 kilometers) west of London, has been used by American bombers during decades of conflicts in the Middle East.

The U.S. military still maintains a sizable presence in the Middle East. On Thursday, a U.S. official said the recently deployed USS Theodore Roosevelt aircraft carrier, as well as the USS Malkin Island amphibious readiness group — a group of ships that together carry over 7,000 sailors and 2,000 Marines — are heading for the region. The official said the move could result in three carriers in the region as early as the end of October.