A car was floating in a dam. It's believed a body had been inside it for 13 years.

A car containing unidentified skeletal remains, which was retrieved from a Queensland dam, belonged to a missing Tasmanian man last seen in the area 13 years ago.

Police say further forensic tests will be needed to confirm whether the bones belonged to Stuart Gatehouse, who was 45 when he vanished during a trip from Kenilworth to Gympie in 2004.

The car he was travelling in, a red 1986 Holden Commodore, was pulled from Borumba Dam near Imbil on Thursday by police, after a member of the public detected a large object near the boat ramp using a depth sounder.

“At this stage it is far too early in the investigation to be making any speculation as to who the deceased person (is) that was located in that vehicle,” Detective Inspector David Drinnen told reporters on Friday.

Police are unsure how the Commodore ended up in the dam.

"We have not been able to establish what has transpired in relation to the vehicle," Det Insp Drinnen said.

Investigations continue.