The remains of US servicemen killed in North Korea decades ago left for home on Wednesday after a solemn ceremony at an American military base in South Korea.
Two US military aircraft took the 55 sets of remains to Hawaii, where historians and scientists will begin a long and complex process of identification.
Pyongyang last week returned the remains from the 1950-53 Korean War, in line with an agreement between US President Donald Trump and its leader Kim Jong Un at their historic summit in Singapore in June.
Trump has praised Kim for "keeping his word" about the handover and said Vice President Mike Pence would meet families when the remains arrive back in the US.
The process of identification could take years, according to experts. But John Byrd, director of scientific analysis at the Defense POW/MIA Accounting Agency (DPAA), said preliminary findings suggested that "they are likely to be American remains".
"The remains are consistent with remains we have recovered in North Korea... in the past," Byrd told reporters at Osan US Air Base in South Korea. The cases had been kept there since Friday, awaiting their repatriation to Hawaii for further forensic analysis.
"There's no reason at this point to doubt that they do relate to Korean War losses," he added.
Around 500 officials from the United Nations Command (UNC), the United States and South Korea attended the formal repatriation ceremony at the airbase on Wednesday.
The cases, each draped with a white and blue UN flag, were lined up in rows as the ceremony got under way.
"This is a solemn reminder that our work is not complete until all have been accounted for, no matter how long it takes to do so," said General Vincent Brooks, the Commander of the UNC and of United States Forces Korea.
After the ceremony uniformed soldiers carefully deposited each case into two C-17 cargo planes, which later took off for Hawaii.
Byrd told reporters that "there was a single dog tag (US soldier's identity tag) provided with the remains".
"The family of that individual has been notified," he said.
"But I would caution... that it's not necessarily the case that the dog tag goes with the remains... in the box," he added, underscoring the challenges of identifying the recovered remains.
The returned material also included military hardware and uniforms, including helmets, water bottles and boots, he said.
DNA, bones, dental records
Former DPAA official Jeong Yang-seung, who previously worked on identifying US remains from the North, said it was unusual to locate dog tags during the search and recovery process.
"It's once in a blue moon that dog tags are recovered," Jeong, now professor of forensic anthropology at the Middle Tennessee State University, told AFP.
"I don't think North Korea is refusing to give dog tags when it has more but it probably doesn't have dog tags lying around," he said.
"So when... only one dog tag was provided, it's probably not to tease the US but rather that it was sent because it could offer clues to the remains."
DNA analysis, skeletal studies of bones, dental records and details of where the remains were found play a key role in such investigations, he said.
"It's a very thorough process with many, many procedures so it takes a long time," he said.
"If it's identified quickly, it would be around five to six months, but if not, it could take decades."
More than 35,000 Americans were killed on the Korean Peninsula during the war and around 7,700 of them are still considered missing, including 5,300 in North Korea alone.
Between 1990 and 2005 229 sets of remains from the North were repatriated, but those operations were suspended when ties worsened over Pyongyang's banned nuclear weapons programme.