North Korea’s media say the death of American college student Otto Warmbier remains a mystery. The statement comes days after the 22-year-old student died in a Cincinnati hospital after returning from North Korean detention where he spent 17 months.

Doctors who treated him upon return to the United States said the former University of Virginia student, who went on an excursion in the reclusive country, had incurred severe brain damage. Doctors called his condition “unresponsive wakefulness.”

North Korea's claim

However, North Korean officials claimed that Warmbier went into a coma after contracting botulism when he took a sleeping pill.

According to CNN, the Warmbier’s family alleges that their son was tortured. Otto’s father, Fred Warmbier said the awful and inhuman treatment their son received from the North Koreans was an indication that no other outcome could have resulted in his death beyond the sad experience they witnessed, he lamented upon the announcement of his son’s death.

On Friday, KCNA News Agency said Otto Warmbier was treated fairly and in accordance with domestic law. It dismissed the claims that he was tortured during his 17 months captivity in North Korea.

The news agency reported that Otto’s sudden death upon his return to the United States in less than a week in his normal health condition was a mystery.

Warmbier was sentenced to 15 years hard labor after being found guilty of committing hostile acts against the state.

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His trial lasted for about an hour. He was arrested at the Pyongyang airport on his way back home in January 2016.

The purported evidence against Warmbier

A video footage of him dismantling a political banner from his hotel room was used as evidence against him. He went on a five-day tour of the isolated country that landed him in detention for 17 months.

Warmbier was not seen in public until the US Department of State learned of his dire state of health on June 6 which prompted his release a week later.

President Donald Trump described the situation a disgrace and said Otto Warmbier should have been sent home a long time ago.

Warmbier's death and burial

He died on Monday, a few days of returning to the United States, and was buried Thursday in his hometown in Ohio. Kenneth Bae, who regained his freedom after spending two years in a North Korean jail, said Warmbier could have been maltreated and tortured. He warned Americans against visiting the pariah state.