The embassy is preparing to give Cpl. Wassef Ali Hassoun back to U.S. military custody. Hassoun, a Lebanese native, apparently went on unauthorized leave from his base in western Iraq 19 days ago. He was assumed to be absent without leave.
However, a videotape of Hassoun was then revealed showing the Marine tied up and blindfolded. His alleged captors threatened to kill him.
After an erroneous claim emerged over the weekend that he had been beheaded, Hassoun was allegedly freed on the condition that he vow not to return to the Marine Corps.
Hassoun is expected to be transferred to Landstuhl air base, Germany, for a medical check-up.
The circumstances of his deparature from base and alleged capture by terrorists is under investigation by the Navy, a Navy source said.
Also Thursday, an apparent gunfight broke out at or near Hassoun's relative's home in Tripoli, according to Arab news reports.