Police have criticised private investigators after they cut bone fragments believed to be linked to the 1973 disappearance of 11-year-old Joanne Ratcliffe and four-year-old Kirste Gordon from Adelaide.
South Australian Police were handed the fragments in July and September 2025 after a bone was found by private investigators and journalist Bryan Littlely.
It was discovered at a property in the small town of Yatina that was owned by a former suspect in the girls' disappearance.
Major crime detectives on Tuesday revealed Micro-CT scanning and a peer-reviewed examination by an expert forensic anthropologist determined the fragments were not human.
The bone handed to police in July 2025 had been cut into five small fragments, prompting a warning from authorities.
Cutting and handling the bone had compromised forensic testing and made it extremely difficult for experts to determine whether it was human, police said.
"If the bone fragment had been human, the way it was handled, cut, and packaged could have significantly hindered the extraction of DNA and may have prevented the identification of a deceased person," a police statement said.
"Such actions have the potential to cause serious detriment to investigations and undue distress to families of missing persons."
Anyone with information about a missing person should contact police immediately, Detective Superintendent Darren Fielke said.
"There are serious criminal offences relating to interfering with human remains and anyone who finds or comes into possession of human remains should contact police as soon as possible," he said.
Mr Littlely said he expected the swift return of the fragments to allow further private investigations and independent testing.
"If it is animal bone, it means only that we have not located human remains during our limited, perfectly legal, exploration of a site our investigations lead us to," he posted on social media.
In 2025, Mr Littlely said the bone was found at the former property of Stanley Arthur Hart, who was previously subject to a police investigation that included searches in the Yatina area.
A forensic anatomist had 90 per cent certainty the bone was part of a small human pelvis, Mr Littlely told 9 News at the time.
On Tuesday, Mr Littlely said he would continue to present potential evidence to police and adhere to their instructions.
Police on Tuesday said they would not conduct further searches in the Yatina area.
Joanne and Kirste were last seen on August 25, 1973, at Adelaide Oval when 13,000 football fans attended a state Australian Rules football match between North Adelaide and Norwood.
The girls had been allowed to leave the Edwin Smith stand to go to the toilet together during the game.
Witnesses reported they may have been seen with an unknown man in his 40s near Port Road in Thebarton.
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