Pyongyang, North Korea (CNN) American college student Otto Warmbier has landed back in the United States after more than 17 months in detention in North Korea.

Warmbier has been in a coma for over a year, according to his parents, and will be rushed to the University of Cincinnati Medical Center late Tuesday, a hospital spokeswoman said.

His return to the US comes as questions swirl about his health and what happened to him while he was detained by the North Korean government. The 22-year-old contracted botulism last year and is in "bad shape,"a source close to the family told CNN. North Korea told a US official that Warmbier contracted botulism and slipped intothe coma after taking a sleeping pill, a senior State Department official told CNN.

"Otto has left North Korea. He is on Medivac flight on his way home. Sadly, he is in a coma and we have been told he has been in that condition since March of 2016. We learned of this only one week ago," said Fred and Cindy Warmbier in a statement.

"We want the world to know how we and our son have been brutalized and terrorized by the pariah regime in North Korean. We are so grateful that he will finally be with people who love him."

Warmbier was detained in January 2016 at the airport in Pyongyang while on his way home. His parents say the University of Virginia student had been on a tour of the reclusive country.

North Korean authorities said they had security footage of him trying to steal a banner containing a political slogan that was hanging from the walls of his Pyongyang hotel.

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That was used as evidence in his hour-long trial , during which North Korea accused him of committing "hostile acts" against the regime at the urging of a purported member of a church in his home state of Ohio, a secretive university organization and the CIA.

Warmbier was found guilty and sentenced in March 2016 to 15 years hard labor. It was the last time he was seen publicly.

North Korea: Warmbier contracted botulism

Warmbier was one of four Americans detained in North Korea.

Since last March, the US had been pressing North Korea to let Swedish officials see the four Americans, the senior State Department official told CNN. When the Swedes finally got the okay to visit, the North Koreans immediately asked for a meeting with Joe Yun, the US envoy in New York, when he was told about Otto Warmbier's condition.

In that meeting about a week ago, Yun was told that Warmbier had contracted botulism a year ago and went into a coma after taking a sleeping pill. US officials then urged those with the ability to persuade Pyongyang to ratchet up the pressure to get him released, said a source, who is familiar with the government's efforts.

A second senior State Department official said the US has not yet accepted the North Korean version of events in terms of the timing and cause of how Warmbier fell into a coma.

"All we know so far is what they have told us," the official said. "This is the North Korean version of events. We won't know anything for sure until doctors are able to fully evaluate Otto's condition."

Three other Americans

Two of the three other Americans being held in North Korea, Kim Sang Duk and Kim Hak-song, are academics who worked at the Pyongyang University of Science and Technology. The third is a businessman named Kim Dong Chul.

Americans detained in North Korea Currently held: • Kim Dong Chul, the president of a company involved in international trade and hotel services, was arrested in 2015 and is serving 10 years on espionage charges. • Kim Sang Duk, also known as Tony Kim, a university professor, was detained in Pyongyang in 2017 and accused of attempting to overthrow the government. • Kim Hak-song, a native Korean born in China (Jin Xue Song is the Chinese version of his name) and professor working at the same university as Tony Kim was detained May 6 on suspicion of "hostile acts" against the regime.

Secretary of State Rex Tillerson said the United States is discussing their respective cases with the North Korean regime. The United States does not have a diplomatic mission in North Korea. "It's a delicate matter, he said. We're working on it."

But their fates have been hanging in the balance as Pyongyang and Washington have seen relations get testier in recent months.

North Korea has fired 16 missiles in 10 tests this year. Experts say each launch gets the country closer to its stated goal of developing a nuclear-armed weapon capable of reaching the United States.

North Korea believes its missile program is the only way to deter Washington from trying to overthrow the regime of Supreme Leader Kim Jong Un.

No connection to Rodman visit

"Otto's detainment and sentence was unnecessary and appalling, and North Korea should be universally condemned for its abhorrent behavior. Otto should have been released from the start," said US Sen. Rob Portman, who represents Warmbier's home state of Ohio. "Fred, Cindy, and the Warmbier family have been remarkably strong throughout this ordeal. Over the last 18 months, they have had to endure more than any family should have to bear."

The news of Warmbier's release comes the same day as basketball star Dennis Rodman arrived in Pyongyang for an expected four-night visit. But there is no connection between the two events, US National Security Council spokesman Michael Anton said.

Rodman isn't representing the US government or serving as President Donald Trump's emissary, Anton said.

When asked if he would bring up the cases of Warmbier and three other Americans detained in North Korea, Rodman told reporters, "that's not my purpose right now ... My purpose is to go over there and try to see if I can keep bringing sports to North Korea."

Rodman had nothing to do with the student's release, said the source familiar with the government's efforts to free Warmbier.

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'We've needed to talk about Otto'

Warmbier appeared emotional at a news conference organized by the North Koreans before his trial in March 2016.

He tearfully confessed to being "lured by the United States administration to commit a crime in this country."

It's not clear if he was forced to speak by the North Koreans.

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His case largely stayed quiet after that until May of this year, when his parents decided it was time to speak out.

When they spoke to CNN on May 3, they said they had not seen or heard from Otto since his supposed confession.

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"With tensions as high as they are, we felt that we needed to talk about Otto and put a face on the person," Cindy Warmbier said.

Despite the increasingly hostile US-North Korean relationship, the Warmbiers said they were encouraged by US President Donald Trump's willingness to improve relations with North Korea.

'I'm excited for him to be back'

Emmett Saulnier, Warmbier's former college roommate, said he got a brief phone call from Warmbier's father early Tuesday to let him know the younger Warmbier was coming home, and he had been in a coma since last March. Saulnier immediately called some of their closest friends.

Saulnier and Warmbier met the summer before their freshman year at Virginia. The two bonded over their Ohio roots, and later lived together their junior year, when Warmbier was detained, Saulnier said. The pair had signed a lease to live together again this past school year, their senior year.

"It's just been so long that he's been there that to hear he is actually coming home was incredible," Saulnier told CNN in a text message.

Saulnier said: "I'm excited for him to be back."