Austin has not relinquished his authority, the Pentagon said.
The rapid notification is in contrast to the delay in notification about his previoushospitalization.
Austin was taken by his security detail to the hospital at approximately 2:20 p.m.
U.S. Defense Secretary Lloyd AustinGetty
ET Sunday, Maj. Gen. Pat Ryder, the Pentagon press secretary, said in a statement.
At this point, Austin has not been admitted to the hospital.
Both the White House and Congress have been notified.
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Deputy Defense Secretary Kathleen Hicks would assume the duties if required.
