The deaths of Pfc. Steven Hodges of Menifee, Calif., and 21-year-old Pfc. Kevin Christian of Haslet, Texas, occurred weeks apart. Pima County Chief Medical Examiner Dr. Greg Hess announced his determination on Thursday.
Hodges was found June 1 near the border city of Nogales; Christian died Sunday, 200 miles away in Ajo.
Both men were assigned to the Southwest Border Support Mission, which has some 2,400 service members.
President Trump has deployed active-duty soldiers to the U.S.-Mexico border to support the Border Patrol amid a surge of migrants from Central America. Duties have included placing hundreds of miles of concertina wire and reinforcing points of entry.
Military officials said the deaths are still under investigation.