Updated March 11, 2017 16:02:03

Police are conducting a land and water search in Brisbane's north in relation to the disappearance of missing 22-year-old man Samuel Thompson.

Photo: Samuel Thompson's disappearance is out of character, police say. (Facebook)

The childcare worker was last seen leaving his Albion apartment on March 7.

The search operation with police and emergency service workers is taking place at Deep Water Bend at Bald Hills.

Investigators are treating the disappearance as a possible homicide after Mr Thompson's car was found unlocked beside a road near Byron Bay in northern New South Wales on Thursday.

Mr Thompson's phone and social media accounts have not been used since he went missing.

Police have said his disappearance was out of character and they held grave fears for his safety.

Detectives said Mr Thompson was close to his family and in good health when he was last seen.

On Friday, Detective Inspector Tim Tresize said Mr Thompson was assaulted by masked men last September when his car was stolen, but later recovered.

Photo: Mr Thompson's orange Ford Mustang was found with the windows wound down near Byron Bay. (Facebook)

"We don't know whether that incident is at all linked to his current disappearance, but obviously we're looking at all possible avenues of inquiry," he said.

Inspector Tresize also said there had been no signs of disturbance at Mr Thompson's apartment.

"He was seen leaving the apartment by himself at 9:30 on Tuesday morning," he said.

"He was by himself and appeared in good health and spirits.

"We have serious concerns about where Sam is and the potential risk to Sam's safety."

Photo: A search operation with police and emergency service workers is taking place at Bald Hills. (Supplied: Moreton Crime Watch)

He said police were tracing phone calls and checking emails and social media conversations.

Inspector Tresize said it was unusual that Mr Thompson left his dog locked in his unit and use of his mobile phone and social media accounts suddenly stopped.

"People do go missing all the time, but normally those people aren't of good physical and mental health, they aren't surrounded by friends and loved ones, and there is usually some explanation and there is a note left and something else," he said.

"In this case, it is a complete mystery.

"Sam, like many young people, uses social media on a regular basis and all that use also stopped on Tuesday."

Photo: Mr Thompson was last seen leaving his apartment at Albion in Brisbane's north on March 7. (ABC News: Kristian Silva)

Topics: missing-person, community-and-society, crime, law-crime-and-justice, brisbane-4000, albion-4010, qld, bald-hills-4036, australia

First posted March 11, 2017 13:09:23