The USS George Washington carrier group, which finished a port visit in Vietnam on August 5, is currently headed to the Middle East to replace the USS Abraham Lincoln, a US official told CNN.

The official said that the swap had been previously planned. It was not immediately clear when the Washington would arrive.

The Lincoln has been the subject of growing concerns about the wellbeing of its crew, with Democratic lawmakers demanding answers from the Pentagon.

CNN first reported on Thursday that a sailor had gone overboard last month, but was quickly rescued and medically evaluated. The circumstances under which the sailor went overboard were not immediately clear nor whether the sailor returned to duty or was evacuated from the ship.

News outlets Stars and Stripes and the Navy Times reported this week that there had been multiple attempts by crew members to jump overboard, citing interviews with sailors and families of those on board who described the impacts of its lengthy deployment.

Since the Lincoln left its home port of San Diego last November, the aircraft carrier has been deployed for more than 250 days after being redirected to the Middle East to support US operations in the war with Iran, now entering its sixth month.

-CNN