Vo Van Tuan, Vietnamese People's Army's deputy chief of staff, told The Wall Street Journal that the crash occurred during a "parachuting exercise."
He also told BBC News that the MI-171 aircraft, which was bought from Russia, crashed due to a technical failure.
Initial reports indicated that the crash had killed 16 people, but three of the injured have since died.
One witness told Voice of America that she saw the helicopter struggle in the air before its fiery crash.
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