WYOMING, Ohio (AP) -- An American college student who was imprisoned in North Korea and returned to his home state of Ohio in a coma suffered a "severe neurological injury," a hospital spokeswoman said Thursday.
Otto Warmbier is in stable condition at the University of Cincinnati Medical Center with his mother by his side, hospital spokeswoman Kelly Martin said. Doctors planned an update later Thursday.
His father, Fred Warmbier, said he does not believe North Korea's explanation that the coma resulted from botulism and a sleeping pill. He said there was no reason for North Korea to keep his 22-year-old son's condition a secret and deny him top medical care.
Fred Warmbier called his son's return bittersweet.
"Relief that Otto is now home in the arms of those who love him and anger that he was so brutally treated for so long," he said at a news conference at Wyoming High School, where Warmbier graduated in 2013 as class salutatorian and played soccer.
To honor his son, Fred Warmbier wore the same jacket Otto wore when North Korea presented him before the media in 2015 at an event where he tearfully confessed that he tried to steal a propaganda banner while visiting the country.
Fred Warmbier said that he doesn't know why North Korea released his son but that the country doesn't do anything out of "the kindness of their hearts." He called on the country to release other Americans currently held there.
"There's no excuse for the way the North Koreans treated our son," he said.
Warmbier also accused North Korea of luring Americans to the country with the false promise they will never be detained.
He said he received "a very nice phone call" Wednesday from President Donald Trump, who said Secretary of State Rex Tillerson worked hard to bring Otto home.
Fred Warmbier told Fox News' Tucker Carlson on Wednesday that Otto was "terrorized and brutalized" during his 17-month detention and has been in a coma for more than a year.
"The day after he was sentenced, he went into a coma," the father said in an interview scheduled to air Thursday night. He said he and his wife, Cindy, only learned of their son's condition last week.
The University of Virginia student was medically evacuated from North Korea and arrived in Cincinnati late Tuesday. He was then taken by ambulance to the University of Cincinnati Medical Center.
Residents of the northern Cincinnati suburb tied blue-and-white ribbons, the school colors, to trees near the family's home. Joy at his release was mixed with concern over his condition.
In its first official comment since Warmbier was returned home, North Korea said it released him for humanitarian reasons. The state-run Korean Central News Agency on Thursday said he had been sentenced to hard labor, but it did not comment on his medical condition.
Bill Richardson, a former U.S. ambassador to the United Nations, called for an investigation into what happened to Warmbier leading to this "tragic situation."
Richardson, a Democrat, credited the State Department with securing Warmbier's return from North Korea without any preconditions but said a forceful response from the U.S. government would be required "if it's determined that there was a cover-up and Otto's condition was not disclosed and he didn't get proper treatment."
Warmbier was serving a 15-year prison term with hard labor in North Korea.
Such detentions in the totalitarian nation have added to tensions between Washington and Pyongyang. Three Americans remain in custody.
The U.S. government accuses North Korea of using such detainees as political pawns. North Korea accuses Washington and South Korea of sending spies to overthrow its government.
Tillerson said Tuesday that the State Department was continuing "to have discussions" with North Korea about the release of the other three imprisoned American citizens.
Associated Press Writer Andrew Welsh-Huggins in Columbus contributed to this report.