The official, who discussed previously undisclosed aspects of the remains issue on condition of anonymity, said it probably will take months if not years to fully determine individual identities from the remains, which have not yet been confirmed by U.S. specialists to be those of American servicemen.

The official did not know details about the single dog tag, including the name on it, or whether it was even that of an American military member. During the Korean War, combat troops of 16 other United Nations member countries fought alongside U.S. service members on behalf of South Korea. Some of them, including Australia, Belgium, France and the Philippines, have yet to recover some of their war dead from North Korea.

The 55 boxes were handed over at Wonsan, North Korea last Friday and flown aboard a U.S. military transport plane to Osan air base in South Korea, where U.S. officials catalogued the contents. After a repatriation ceremony at Osan on Wednesday, the remains will be flown to Hawaii where they will begin undergoing in-depth forensic analysis, in some cases using mitochondrial DNA profiles, at a Defense Department laboratory to attempt to establish individual identifications.