Police in the United States city of Atlanta say an investigation into the disappearance of a 20-year-old Perth man is “advancing rapidly”.

Mohammad “Naz” Rahimi was holidaying in Atlanta when he disappeared 22 days ago.

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In a statement sent to the ABC Atlanta police said he was reported missing on March 31 and was last seen on foot near the Morningside Nature Reserve.

The statement said he was due to return to Perth on April 11.

The ABC was told Mr Rahimi was sleeping on a friend’s couch.

His mobile phone and iPad were later seen beside a creek, but by the time police tried to retrieve them they had disappeared.

Atlanta police said the investigation into his disappearance is advancing rapidly, but they can not release any further details at this time.

Naz was due to take a flight back from the US to Perth on April 11. Photo: ABC