Image copyright Reuters

The coroner who examined Otto Warmbier's body has said there is no clear indication he had been tortured during his detention in North Korea.

The comments contradict statements made by the US student's parents in a TV interview with Fox on Tuesday.

They said North Korea had "systematically tortured" their son after he was jailed for stealing a sign during a holiday in Pyongyang in 2016.

The Ohio county coroner said he had died from lack of oxygen to the brain.

"We don't know what happened to him and that's the bottom line," Dr Lakshmi Sammarco said in a news conference on Wednesday.

Otto Warmbier died in June shortly after being released by North Korea on medical grounds. He arrived home in a state of "unresponsive wakefulness".

North Korea said he contracted botulism shortly after being sentenced, but US doctors have disputed this.

'No evidence of dental trauma'

In their interview with Fox and Friends, Fred and Cindy Warmbier said when they first saw him on his return, their son was "jerking violently" and made "inhuman sounds".

Image copyright other Image caption Otto Warmbier (far right) had travelled to North Korea with an American tour group

They said his arms and legs were "totally deformed", he had a scar on his foot that had been an open wound for some time, and his bottom teeth looked "like someone had taken a pair of pliers" to them.

"Otto was systematically tortured and intentionally injured by Kim and his regime," said Mr Warmbier.

Dr Sammarco conducted an external examination and scans of Mr Warmbier's body - his parents refused a post-mortem.

She said she was "surprised" by the Warmbiers' statement.

"I felt very comfortable that there wasn't any evidence of trauma" to the teeth, she told reporters. There were only small scars on his body, including his foot. One of the scars could not be explained.

But she said his body and skin were in "excellent condition" for someone who had been bedridden for more than a year.

She said he died from lack of oxygen and blood to the brain caused by an injury more than year before.

Muscle spasms, eye movements and noises can all be consistent with oxygen deprivation.

US President Donald Trump had called the Warmbier's appearance "a great interview", and said "Otto was tortured beyond belief".