SEOUL, South Korea >> The U.S. military said it moved 100 wooden coffins to the inter-Korean border to prepare for North Korea’s returning of the remains of American soldiers who have been missing since the 1950-53 Korean War.

U.S. Forces Korea spokesman Col. Chad Carroll also said Saturday that 158 metal transfer cases were sent to a U.S. air base near Seoul, South Korea’s capital, and would be used to send the remains home.

North Korea agreed to return U.S. war remains during the June 12 summit between North Korean leader Kim Jong Un and President Donald Trump. While the U.S. military preparations suggest that the repatriation of war remains could be imminent, it remains unclear when and how it would occur.

Earlier Saturday, Carroll denied a report by South Korea’s Yonhap news agency that U.S. military vehicles carrying more than 200 caskets were planning to cross into North Korea on Saturday. He said plans for the repatriation were “still preliminary.”

U.S. Forces Korea said in a statement later in the day that 100 wooden “temporary transit cases” built in Seoul were sent to the Joint Security Area at the border as part of preparations to “receive and transport remains in a dignified manner when we get the call to do so.”

From 1996 to 2005, joint U.S.-North Korea military search teams conducted 33 recovery operations that collected 229 sets of American remains.

But efforts to recover and return other remains have stalled for more than a decade because of the North’s nuclear weapons development and U.S. claims that the safety of recovery teams it sent during the administration of former President George W. Bush was not sufficiently guaranteed.

U.S. officials have said earlier that the remains are believed to be some or all of the more than 200 that the North Koreans have had for some time. But the precise number and the identities — including whether they are U.S. or allied service members — won’t be known until the remains are tested.

The transfer of remains is usually done in a somber, formal ceremony, and that is what officials said was being planned.

Richard Downes, executive director of the Coalition of Families of Korean & Cold War POW/MIAs, said last week that he had been told the North may have the remains of more than 200 American service members that were likely recovered from land during farming or construction and could be easily returned. But he said the vast majority have yet to be located and retrieved from various cemeteries and battlefields across the countryside.

More than 36,000 U.S. troops died in the conflict, including those listed as missing in action. Close to 7,700 U.S. troops remain unaccounted for from the Korean War, and about 5,300 of those were lost in North Korea.

The last time North Korea turned over remains was in 2007, when Bill Richardson, a former U.N. ambassador and New Mexico governor, secured the return of six sets.

According to Chuck Prichard, spokesman for the Defense POW/MIA Accounting Agency, once the remains are turned over, they would be sent to one of two Defense Department facilities — Joint Base Pearl Harbor-Hickam in Hawaii and Offutt Air Force Base in Nebraska — for tests to determine identification.