Homicide detectives are investigating the discovery of human bones in the Royal National Park, south of Sydney.

The skeletal remains were found by a driver who pulled up on the side of Sir Bertram Stevens Drive on Saturday afternoon.

Police established a crime scene and began conducting line searches of the park on Sunday.

A source told the ABC that the bones were human, but a gender or age was yet to be determined.

It is believed that the bones had been buried in the park for quite some time before the discovery was made.

Forensic investigators are now working to identify the person, possibly looking at DNA and dental records.

While police found the bones of Matthew Leveson in the same park last year, it is believed the latest discovery is unrelated.

The Cronulla man was last seen leaving ARQ nightclub in Darlinghurst with his ex-boyfriend Michael Atkins 11 years ago.

Mr Atkins took police to the burial site after he was offered immunity from prosecution for perjury and contempt of court.

Anyone with information, or who has seen anything suspicious in the Royal National Park, is being urged to contact Crime Stoppers.