Among those detained are three missionaries who were sentenced to hard labor for life on charges of working for South Korea's spy agency.
Doctors who examine Mr Warmbier after his release said there was no sign of botulism in his system.
His family said last week they were told he had been a coma since soon after his March 2016 sentencing. He returned 17 months later in a #coma on June 13, 2017.
His parents, Fred and Cindy Warmbier, said in a statement that he died surrounded by loved ones at 2:20 p.m. on Monday.
His parents explained that when Warmbier returned to Cincinnati, he was "unable to "see", "speak" and "react to verbal commands".
"Unfortunately, the bad torturous mistreatment our son received at the hands of the North Koreans ensured that no other outcome was possible beyond the sad one we experienced today", the family said in a statement after Warmbier's death at 2:20 p.m.
Korean Americans Tony Kim and Kim Hak Song who worked at the foreign-funded Pyongyang University of Science and Technology (PUST) were recently detained for hostile acts against the state, according to North Korea's state media. He was leaving the country on January 2 a year ago when he was detained at the airport. He said North Korea had demanded the return of 13 North Korean workers "resettled in Seoul", as a precondition to further talks on reunions, halted in October 2015. He is believed to have slipped into a coma shortly after his trial.
Moon, who was elected on a plan to engage in talks with North Korea, said he agreed with Trump on being willing to participate in a dialogue with North Korea under certain conditions, given that sanctions and global pressure have not resolved the situation.
They said Warmbier's severe brain injury was most likely - given his young age - to have been caused by cardiopulmonary arrest cutting the blood supply to the brain.
A spokesman for the Hamilton County coroner says Dr. Lakshmi Sammaraco's (LAK'-schmee sam-MAHR'-rahk-oh) office has accepted the case of Otto Warmbier, who died Monday in a Cincinnati hospital.
A month after his arrest, he appeared at a news conference tearfully confessing to trying to take a sign from his hotel as a "trophy" for a U.S. church.
"China hopes that joint efforts with the United States will promote dialogue and achieve positive results", he said, adding that Beijing "hopes to continue communication and cooperation with the USA and relevant parties" to work towards denuclearisation of the Korean Peninsula.
Young Pioneer Tours said on its Facebook page Tuesday that the death of the 22-year-old Warmbier shows that the risk American tourists face in visiting the isolated nation "has become too high". The group said it was denied requests to meet Warmbier or anyone who'd been in contact with him in Pyongyang, only receiving assurances that he was fine.
Warmbier was medically evacuated from North Korea on June 13 following diplomatic talks at the top of the US government.
The guy fell into a coma after she took sleeping pills.
Warmbier's family said they believed the student had found peace after being flown home.