A Rockwell B1 Lancer heavy bomber takes off from RAF Fairford in Fairford, United Kingdom, on October 04. - David Bown/Getty Images

The United States has moved long-range bombers back to their American home stations after an unspecified new threat, according to a US official, days after the British government arrested a number of individuals in connection with an alleged Iranian plot to target the UK airbase where the planes had been stationed.

“We can acknowledge now that all U.S. bombers that were deployed to RAF Fairford have re-deployed to their home stations in the United States,” the official told CNN. The statement did not include details on why the plan...