The White House said it did not comment on intelligence, Reuters reported, while a senior official at South Korea's presidential office said USA and South Korean intelligence agencies are closely looking into various North Korean movements.
General Kim Do-gyun, the South's chief negotiator who is in charge of North Korea policy at the Ministry of Defense, said Tuesday's talks were meaningful in "creating understanding" in ways to implement the summit agreement.
After racing toward his goal of developing a nuclear-tipped missile capable of striking the continental United States, Kim said in April that he had shifted his country's focus to the economy.
Hundreds of USA and South Korean troops gathered at a hanger at the Osan base for the repatriation ceremony, which included a silent tribute, a rifle salute and the playing of the United States and South Korean national anthems and dirges in front of the UN flag-covered metal cases containing the remains.
"Keep in mind that it's not necessarily the case that" the person identified in the dog tag will be among the remains but they're hopeful, he said.
"That's why the first step the intelligence community is probably looking for is a complete declaration of nuclear and missile related facilities - to see if North Korea includes everything they already know about or suspect", he said.
North Korea only provided one military dog tag along with the boxes, according to The Associated Press.
The 55 flag-draped boxes of remains from potential prisoners of war were returned to the U.S. on Friday.
Skywatchers looking forward to complete lunar eclipse
But, while there was a spectacular sunrise, the eclipsed moon disappeared behind low cloud at the crucial moment in Christchurch. Where can you see the blood moon in July 2018? You'll have to stay inside (where it's safe) and instead watch it online.
The U.S. Defense Department estimates that about 7,700 American service members were missing during the Korean War from 1950 to 1953.
Byrd said the preliminary findings of the American investigation were that the remains are what North Korean officials said they were.
North Korean leader Kim Jong-un also vowed during the June 12 summit with US President Donald Trump in Singapore to work toward denuclearization, but there has not been a concrete agreement to accomplish that goal.
But some independent analysts think the Trump administration has misread Kim's intentions, interpreting his commitment to eventual denuclearization as a promise to immediately surrender the country's nuclear arsenal and dismantle its weapons factories.
The Pentagon estimates that almost 7,700 US troops are unaccounted for from the war; among them are 5,300 believed to have been killed north of the 38th parallel, which largely follows the boundary between North and South Korea.
Since Trump returned from that trip to tell America to "sleep well", North Korea has expanded production of nuclear materials and improved facilities for building missiles. But many experts say those are neither irrevocable nor serious steps that could show the country is honest about denuclearization.
Intelligence collected by United States agencies showed, however, that senior North Korean officials have discussed plans to deceive Washington about the number of nuclear warheads and missiles they possess, as well as the types and number of facilities, and to rebuff global inspectors, according to the Post.
These officials say new evidence, including satellite photos taken in recent weeks, suggests that work is under way on at least one and possibly two liquid-fueled intercontinental ballistic missiles at a research facility in Sanumdong on the outskirts of Pyongyang.
The Department of Defense is beginning the long and hard task of identifying the remains turned over to the United States from North Korea. Experts say the North likely wants a declaration of the end of the Korean War as part of US security assurances.
Since the Singapore summit, independent researchers and USA intelligence reports published by news organisations have suggested that North Korea is still expanding its weapons programme. The two sides remain technically at war because a peace treaty was never signed.