U.S. officials have sent what are believed to be the remains of at least three American servicemen killed during the Vietnam War to the United States for identification.

Army Lt. Col. Patrick Keane of the U.S. command in Hanoi whose job is to account for Americans missing in action says the remains are believed to be those of servicemen killed in plane crashes. They were recovered in the past month in three central Vietnamese provinces - Nghe An, Quang Binh and Quang Nam.

A repatriation ceremony took place Friday at Danang International Airport.

According to the U.S. office, 689 sets of remains have been repatriated from Vietnam since the war ended in 1975. Another 1,664 Americans are still unaccounted for from the war, including 1,282 in Vietnam.