One of Australia's leading criminologists has revealed the heartbreaking clues that police would have been looking for inside Cleo Smith's family home.
Police have now ruled out the missing 4-year-old's parents as suspects after a third search of the home in Carnarvon on Wednesday.
Dr Xanthe Mallett said investigators would have likely been looking for "signs of injuries or struggles" inside the home.
"It's just to rule out any kind of potential issues that may have happened at home, but certainly the family have been ruled out as suspects at this time, that was stated yesterday so really they are covering their bases to make sure they have all the information going forward," she told Sunrise.
"You would have to look at the family, that would be part of the investigation sadly. Along with all of the avenues that they will be investigating.
"They need to make sure that they collect the evidence that may be available at the beginning so it is not lost so I'd certainly expect them to search that family property as part of any routine investigation."
It has now been 13 days since Cleo vanished which Mallett said was a "really long time in a missing child investigation".
"Obviously she could be anywhere in the country, had she been abducted," she said. "It is a significant worry and every day that passes, obviously getting more concerned for her safety."
It comes as the Australian Federal Police have joined the search for Cleo.
Prime Minister Scott Morrison revealed the agency's involvement in the suspected abduction case on Tuesday, saying he hoped the AFP's "very advanced capabilities" would help the investigation.
"I'm very pleased to say that they're helping in every way they possibly can through their intelligence capabilities, their technology and their forensics abilities," he said.
"I just hope we can find Cleo ... I think the whole nation is just waiting and hoping and praying.
"I just want to assure everybody over there in WA, particularly the family and friends of poor Cleo, this is really capturing the minds of the country."
Creepy warning from Cleo campsite
A sinister warning of an attempted abduction emerged more than seven years ago from the remote campsite where Cleo was last seen.
The social media post on a local Carnarvon chat page raised concerns about a child being approached by a man at the Blowholes campsite.
The local said the girl was approached by a "male aged in his late 40s with a beard" and who was driving a "small red car" at the popular coastal campground in July 2014. The girl's mother said she reported the incident to the police at the time.
"ATTENTION PLEASE BE AWARE …" the mother's post started. "The man asked her if she would get in the car and go for a drive.
"She said no and took off straight back to camp. Sorry I don't have a better description as she was quite freaked out.
"The police have bn [sic] notified. Good time to remind our precious one [sic] of stranger danger."
Police believe that Cleo was abducted after she vanished from a tent she shared with her mother Ellie Smith, stepfather Jake Gliddon and baby sister Isla on October 16.
She had woken about 1.30 am and her mother gave her a sip of water and she went back to bed. When they woke at about 6am, the tent's zipper was open to a height the little girl would not be able to reach and she was gone. Her sleeping bag was also missing.
Last week it was revealed by police that up to 20 registered sex offenders live in the Carnarvon area, all of whom have been interviewed by police.
At this stage, police have not named any suspects in the little girl's disappearance.
Anyone with information about Cleo's disappearance is urged to contact Crime Stoppers on 1800 333 000.