A child sex offender is said to have been identified as a suspect in the murders of Karlie Pearce-Stevenson and her young daughter Khandalyce.
The man is serving a four-and-a-half year sentence in Cessnock Prison, and has previously spent time in jail on child sex offences, Nine Network has reported.
He was reportedly interviewed at a local police station last week, and has since been returned to the jail's maximum security wing.
An NSW Police spokesman was unable to confirm or deny the claims on Saturday, saying the only details available were those released by Homicide Squad Commander Mick Willing on Friday.
Det Supt Willing said investigators were pursuing "a very strong line of inquiry" and had spoken to several violent offenders in NSW prisons, and searched homes in South Australia and the ACT.
"We've looked at and are now speaking to people who we suspect have actual knowledge of what occurred to this young mum and her little girl," he said.
The investigation is moving quickly and detectives are hopeful of a swift arrest.
Karlie is believed to have been killed sometime around December 2008, in or near the Belanglo State Forest where her body was discovered in 2010.
Where and when her daughter Khandalyce died, and how her remains came to be discovered alongside a South Australian highway in July this year is still a mystery.
The pair were last seen in a 1996 red or maroon VL Commodore station wagon near Coober Pedy in November 2008.
"We still believe that friends and associates, people Karlie may have met or been in contact with while travelling between 2006 and 2010, hold the key to their deaths," Det Supt Willing said.
