However, Hamilton County Coroner Dr. Lakshmi Sammarco said Wednesday her office was unable to determine what caused the brain damage that led to Warmbier's death, other than it stemmed from oxygen deprivation more than a year before his death.
But North Korea denied the torture claims and instead accused the United States of "luring and pushing" Mr Warmbier into breaking the regime's rules.
She said he died from lack of oxygen and blood to the brain caused by an injury more than year before.
The coroner also found Otto's overall condition to be "well-developed, well-nourished", noting only there had been a collection of scars on his body.
North Korean authorities accused Warmbier of stealing a poster from a hotel room while he was visiting the isolated country in 2016 and sentenced him to 15 years of hard labor.
"We walked over to the plane, the engines are still humming, they had just landed...when we got halfway up the steps we heard this howling, involuntary, inhuman sound", Fred Warmbier said. "We were surprised at [the parents'] statement".
North Korean officials have said Warmbier was released on humanitarian grounds and had been treated respectfully.
"We don't have enough information about what happened to Otto, that initial insult, to draw any conclusions", Sammarco added.
While Warmbier's family declined an autopsy, Sammarco said her office used extensive medical scanning and imaging for a "virtual autopsy" and that nothing more would have been gained by doing an autopsy so long after his brain damage occurred. On the coroner's report, Warmbier's manner of death is listed as "undetermined".
Fred and Cindy Warmbier said the reality of their son's injuries were much worse than they imagined and insisted Kim Jong Un's regime tortured him until the point of no return.
The report - an external examination, not an autopsy - describes a 4.3-by-1.6-inch scar on Warmbier's right foot.
Otto's hands and legs were "totally deformed", he said, and "it looked like someone had taken a pair of pliers and rearranged his bottom teeth". "They are not victims, they are terrorists", Fred Warmbier said on the program "Fox and Friends".
Warmbier's parents could not be reached for comment on the coroner's report.
"Great interview on @foxandfriends with the parents of Otto Warmbier: 1994 - 2017". Investigators only documented a few smalls scars to his body, and did not find evidence of any healing fractures that would have happened while he was in North Korea, Sammarco said. They tortured him. They intentionally injured him.
A virtual autopsy was performed instead, which does not involve making cuts to the body, Sammarco said.