Austin, 70, was taken back to Walter Reed by his security detail at 2:20 p.m. Sunday, according to Air Force Maj. Gen. Pat Ryder, the Pentagon press secretary. Just before 5 p.m., he transferred his authority to Deputy Defense Secretary Kathleen Hicks.
He remained at the hospital Sunday evening, Ryder said.
Unlike his previous hospitalization that began Jan. 1, Austin notified the White House, Congress and Pentagon officials, Ryder said in a statement.