Republican Sen. Richard Lugar of Indiana says the United States has an “ongoing obligation” to identify the remains of Korean War service members interred at Punchbowl National Cemetery. But it may be impossible to determine the DNA from hundreds of sets of remains.

According to a report Lugar commissioned from the Congressional Research Service, 867 unidentified Korean War soldiers were buried at Punchbowl — most of them on Memorial Day in 1956. Of that total, 416 were turned over by North Korea and  451 came from South Korea graves recovery efforts.

“Since then, 22 have been disinterred: one was transferred to the Tomb of the Unknowns in Arlington National Cemetery, 13 have been accounted for, and 8 are currently being processed for identification by the Joint Prisoner of War/Missing in Action Accounting Command (JPAC) in Honolulu.”

DNA in the 845 sets of remains still at Punchbowl is thought to be uninterpretable, according to the report. It is thought that formaldehyde used to preserve the remains in the 1950s damaged DNA sequences past the point of interpretation. 

According to the report, JPAC researchers will rely on using dental records and collar bone records to identify the service members. 

There are approximately 34,000 American military veterans from World War II, the Korean War and Vietnam interred at Punchbowl, along with 10,200 authorized family members.