Defense Secretary Jim Mattis has welcomed the return of the 55 boxes but acknowledged it's not certain who is inside.
"Problems such as inability to get DNA from bones and lack of a DNA reference sample from the family can be major stumbling blocks", said Chuck Prichard, director of public affairs for the Defense POW/MIA Personnel Accounting Agency, the us military's main unit for finding and identifying missing members.
USA intelligence officials familiar with Pyongyang's operations say that new evidence, including recent satellite photos, suggests that the regime is producing at least one liquid-fueled ICBM at the Sanumdong research facility, near Pyongyang.
He also confirmed a single military dog tag was provided with the remains and that the family of that soldier has been notified.
Pompeo, at the Senate hearing last week, sought to assure lawmakers that the disarmament talks with North Korea remained on track and that the effort to dismantle the country's nuclear arsenal was just getting underway.
Sixteen other countries sent troops to fight in the 1950-53 Korean War under the United Nations umbrella, and several of them also are believed to have been lost in the North.
The repatriation is a breakthrough in a long-stalled US effort to obtain war remains from North Korea.
About 7,700 USA soldiers are listed as missing from the Korean War, and 5,300 of the remains are believed to still be in North Korea.
The Trump administration downplayed reports Tuesday that North Korea is engaged in a flurry of new intercontinental ballistic missile activity, asserting the activity has not undermined President Trump's high-stakes diplomatic outreach to Pyongyang.
On July 27, North Korea returned the remains of US soldiers killed in the Korean War (1950-1953) for the first time in 11 years, a decision warmly welcomed by Washington.
Trump last week thanked Kim for keeping the promise he made as part of their talks about North Korea's denuclearization. National anthems of the United States and South Korea were played, and the caskets were given a 21-gun salute by US riflemen.
Space launch vehicles were assembled at the shelter - which hadn't been moved since December 2017 - before they are moved to the launchpad, according to 38North analyst Joseph Bermudez Jr. But many experts say those are neither irrevocable nor serious steps that could show the country is honest about denuclearization.
U.S. spy agencies have detected signs of North Korea building new intercontinental ballistic missiles at a plant near Pyongyang, the Washington Post reported Monday.
Numerous fallen service members died in North Korea and were buried by their comrades where they fell.
"There are chance encounters, there are sometimes planned encounters - but we're not there yet for any announcement", the official said.
The Netherlands contributed 4,700 soldiers to United Nations efforts to end the Korean war of 1950 to 1953.
How many US servicemen are missing from the Korean War?
Efforts to recover remains in North Korea have been fraught with political and other obstacles since the war's end.
It's possible that questions about the identities of the remains could persist for years to come. Indonesia guarantees the security of all countries' representatives and contingents, including those of North Korea.
Between 1990 and 2005, 229 sets of remains were returned to the USA, but co-operation halted as relations deteriorated alongside the development of North Korea's nuclear programme.