"We are encouraged by North Korea's actions and the momentum for positive change," The White House said.
North Korea turned over the alleged remains of U.S. soldiers who were killed during the Korean War of the 1950s on Friday, the 65th anniversary of the armistice that ended the fighting, the White House said.
"Today, the Chairman is fulfilling part of the commitment he made to the President to return our fallen American service members," a statement from the White House released Thursday night ET said, referring to North Korean leader Kim Jong Un.
"We are encouraged by North Korea's actions and the momentum for positive change," the White House said.
A U.S. transport aircraft flew from Osan Air Base in South Korea at about 6 a.m. (5 p.m. ET Thursday) to Kalma Airport in the eastern North Korean city of Wonsan at about dawn to retrieve the remains, the South Korean news agency Yonhap reported.
The White House said that a U.S. Air Force C-17 aircraft containing the remains of fallen service members departed Wonsan, North Korea.
The plane will take the remains to South Korea and a formal repatriation ceremony will be held on Aug. 1, the White House said. The remains were accompanied by technical experts from the Defense POW/MIA Accounting Agency. The statement did not say how many remains were returned.
The return is part of an agreement reached during the June summit between President Donald Trump and North Korean leader Kim Jong Un.
The transfer sets off a lengthy series of forensic examinations and tests to determine if the remains are human, and whether they are actually American or allied troops killed in the conflict.
About 7,800 U.S. service members were lost and unrecovered from the Korean War, and about 5,300 of those were lost in North Korea, according to the Defense Department. The war, fought from June 25, 1950 until July 27, 1953, is sometimes referred to as "The Forgotten War."
One hundred wooden temporary transit cases were moved into the demilitarized zone separating the two Koreas to receive the remains last month, U.S. Forces Korea said at the time.
Joint U.S.-North Korea military search teams collected 229 sets of U.S. remains from 1996 to 2005. But efforts to recover and return more remains stalled for more than a decade as Washington and Pyongyang clashed over North Korea's nuclear weapons program. The United States, meanwhile, alleged that the safety of its recovery teams wasn't being guaranteed.
South Korea President Moon Jae-insaid Wednesday during a meeting with Harry Harris, the new U.S. ambassador to Seoul, that the transfer of the remains would boost momentum for talks on the North's nuclear program.
More than 33,000 U.S. service members died in battle during the Korean War, the Defense Department has said.
Historians had previously put the number of U.S. service members who died during the war at more than 54,000, but the Defense Department in 1993 divided that larger number into 33,686 battle deaths, 2,830 non-battle deaths in Korea, and 17,730 other deaths across the military, according to a 2000 American Forces Press Service article posted on the department's website.
"It is a solemn obligation of the United States Government to ensure that the remains are handled with dignity and properly accounted for so their families receive them in an honorable manner," The White House said.