"It's my understanding that he is in fact either en route or back in the United States," spokeswoman Marie Harf told reporters when asked about the whereabouts of the officer.
But she gave no further details about the case which has been shrouded in secrecy.
The American spy, Bob Seldon Lady, was convicted in absentia along with 22 other CIA agents in 2009 by Italian authorities over the kidnapping of an Egyptian imam.
The Italian justice ministry announced Lady's detention in Panama yesterday but it was unclear when he was taken into custody or whether he remained a CIA employee.
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The former head of the CIA station in Milan, now 59, received the heaviest sentence, which was increased from eight to nine years on appeal in 2010.
The case was one of the world's biggest to take aim at Washington's controversial "extraordinary rendition" programme, which was set up in the wake of the September 11, 2001 attacks to capture and interrogate suspected Islamist militants.
The United States has said little about the case and refused to extradite the Central Intelligence Agency officers.
When asked about the latest developments in the case, the CIA declined to comment on Friday.