JOINT BASE PEARL HARBOR-HICKAM, Hawaii—The U.S. has identified the remains of two service members among the 55 boxes returned by North Korea this summer, officials from the Defense POW/MIA Accountability Agency said Monday.

After the U.S. military informs family members, it plans to announce their names in the coming days, the officials said. Both service members died in late 1950 near the Chongchon River, in present-day North Korea, where the U.S. suffered heavy casualties, DPAA officials said.

The...