Hiker claims he spoke with Gabby Petito's missing partner in US

A US hiker has claimed he saw Gabby Petito's missing partner Brian Laundrie driving along the Appalachian Trail.

Dennis Davis told Fox News he only realised the man may have been Mr Laundrie after the encounter.

Mr Davis said he had been performing a u-turn in his car and stopped to talk to the driver of the car behind him which had allowed him to make the turn.

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"I could tell right away that something wasn't right with him," he said.

Mr Davis told Fox the man had appeared "mentally shot".

He claimed the man had told him he was trying to get to California to see his girlfriend after they had a fight.

It was only after the other driver departed that Mr Davis wondered if it may have been Mr Laundrie, and he called the FBI after looking up photos of the fugitive on his phone.

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Police searched the area but found no trace of Mr Laundrie.

Mr Laundrie, 23, is wanted for alleged debit card fraud and is a person of interest in the investigation of the death of his partner, 22-year-old Gabby Petito.

The pair were travelling across the US in a van before Mr Laundrie returned to his family's home in Florida on September 1, without Ms Petito.

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She was reported missing on September 11.

Mr Laundrie allegedly refused to cooperate with investigators, and was later reported missing on September 17.

Ms Petito's body was discovered in a Wyoming national park on September 19.

Her death has been ruled a homicide.

Mr Laundrie has not been named a suspect in her death.