Human remains found inside a septic tank at a property in Brisbane's north a fortnight ago have been identified as belonging to a man who disappeared from a house on the site in 1986.

Police said dental records helped them identify 29-year-old Wayne Youngkin.

Two weeks ago, his remains were found by maintenance workers in a disused tank, which sits along the border of a school yard and a property now owned by Autism Queensland, on North Road at Brighton.

Inside the tank, police also found a ring, clothes, and a gold watch inscribed with Mr Youngkin's initials.

Detective Superintendent Mick O'Dowd said Mr Youngkin's disappearance was not widely reported at the time as it was thought he may have just moved away.

"From best our records show, there may have been a period of time where people didn't necessarily believe him to be missing but over the passage of time that became the case and he was reported to police in due course," Detective Superintendent O'Dowd said.

Police suspicious from outset

He said police were still treating the case as a homicide and detectives were trying to track down a member of the public who called the Sandgate Police Station in 1992, suggesting Mr Youngkin was killed.

"The way it presented itself to police in the first instance, was quite obviously suspicious from the outset and we have treated this as a murder investigation since that time," he said.

Before his disappearance, Mr Youngkin was living in a house on the land at Brighton with his grandmother and uncle.

Detective Superintendent O'Dowd said those relatives have since died but police have tracked down Mr Youngkin's cousin as his next-of-kin.

The cause of death is yet to be determined as scientific officers and the coroner continue their investigations.