The remains have not been identified.
Phat says authorities also found 17 pairs of rubber sandals and 23 hammocks among the remains.
He says the soldiers were believed to have been killed while attacking an airport in 1969.
Some three million Vietnamese and 58,000 Americans died during the war, which ended in 1975 when communists overran Saigon, then capital of South Vietnam.
The remains of around 300,000 North Vietnamese soldiers have yet to be recovered.