An American student who had been imprisoned in North Korea for 17 months died from lack of oxygen and blood to the brain, an Ohio coroner said on Wednesday.
Otto Warmbier's death on June 19 was due to an unknown injury that occurred more than a year before his death, Hamilton County Coroner Dr. Lakshmi Sammarco said at a news conference.
"We don't know what happened to him and that's the bottom line," Sammarco said.
Warmbier's parents could not be reached for comment on the coroner's report.
The University of Virginia student was held by North Korea from January 2016 until his release on June 15. Warmbier, 22, returned to the United States in a coma.
Both the investigator and the coroner's report cited complications of chronic deficiency of oxygen and blood supply to the brain in Warmbier's death. Only an external examination of the body rather than a full autopsy was completed at the request of Warmbier's family.
North Korea previously blamed botulism and the ingestion of a sleeping pill for Otto Warmbier's problems, and it dismissed torture claims.
The release of the autopsy report comes at a time of high tension between the United States and North Korea, which is working to develop nuclear-tipped missiles capable of reaching the U.S. mainland.
When Warmbier was brought back to the United States, U.S. doctors said he had suffered extensive brain damage, and he died days later. The native of Wyoming, Ohio, near Cincinnati, was arrested during a tourist visit to the reclusive communist country.
Warmbier was traveling with a tour group when he was arrested at the airport as he prepared to depart from North Korea's capital, Pyongyang.
He was sentenced to 15 years of hard labor for trying to steal an item bearing a propaganda slogan from his hotel, North Korean state media said.
Warmbier's parents appeared on Fox News on Tuesday, calling North Korea "terrorists" who tortured their son.
"It looked like someone had taken a pair of pliers and rearranged his bottom teeth," Fred Warmbier told Fox.
"Great interview on @foxandfriends with the parents of Otto Warmbier: 1994 - 2017. Otto was tortured beyond belief by North Korea," President Donald Trump said on Twitter following the interview's broadcast.
However, the coroner's report said Warmbier's teeth were "natural and in good repair."
Warmbier's body had multiple scars varying in size, including a large irregular one measuring 11.5 by 4 cm (4.3 by 1.6 inches) on the right foot, the report said.