Officials this month have started to exhume the unidentified remains of USS Oklahoma crew members killed in the 1941 Japanese bombing of Pearl Harbor as part of an effort to account for sailors and Marines still classified as missing.

Four caskets were dug up last week and six this week, said Gene Maestas, a spokesman for the National Memorial Cemetery of the Pacific.

The Defense POW/MIA Accounting Agency announced the exhumations in April, saying advances in forensic science and genealogical help from families have made it possible to identify remains nearly 75 years after the attack.

Officials expect to disinter 61 caskets at 45 grave sites at the Honolulu cemetery commonly referred to as Punchbowl, Maestas said Tuesday. These graves contain the remains of up to 388 Oklahoma sailors and Marines because many of the coffins include multiple people.

Altogether, 429 on board the World War II battleship were killed. Only 35 were identified in the years immediately after.

The cemetery and the Defense POW/MIA Accounting Agency declined to allow media to cover the disinterments.

Maestas said an honors detail drapes each casket with an American flag once it is raised out of the ground. He said it’s done in a solemn, dignified manner.

“It really is an honor and a privilege for us to be involved in this process, providing closure for the family members that have waited close to three-quarters of a century to have the remains of their loved ones returned to them,” Maestas said.

Maj. Natasha Waggoner, a spokeswoman for the Defense POW/MIA Accounting Agency, said the identification work will be conducted at agency laboratories in Hawaii and Nebraska. They will also be done at the Armed Forces DNA Identification Laboratory at Dover Air Force Base in Delaware.

The agency expects to identify about 80 percent of Oklahoma crew members now considered missing. It expects the work will take about five years.