The four-year-old is believed to have been abducted from a tent while camping with her family at a remote campsite north of Carnarvon.
Forensic investigators could be seen on Wednesday collecting soil samples from a number of campfires near the shacks in the area.
And forensics officers have also gone back to the family’s home in Carnarvon.
They returned after spending several hours at the property on Tuesday.
Acting Police Commissioner Col Blanch had said Cleo’s parents had been co-operative.
“I must be very clear, so that people don’t make assumptions on this,” he said.
“That is standard practice in any investigation.
“We must do a thorough investigation, the parents have been nothing but helpful.
We’ve worked very closely with them.
“They’ve let us into their home, let us into their car, phones, everything. That is a normal part of investigation and we must follow it through thoroughly.”
Information was still being sought about a car that was seen during the early hours of the same morning Cleo was reported missing.
If anyone saw car movements at or around 3am heading south on the coastal highway from Blowholes Road, that is one of our investigative areas of focus.
“It’s not to say we’re saying that is the person.
“But, certainly, driving around at 3.00, coming out of there would pique our interest.”
Acting Commissioner Blanch said it was important to have hope that Cleo could be brought home.
WA Police have also renewed their plea for businesses in Carnarvon to provide them with any CCTV footage recorded in the days surrounding the disappearance of Cleo on Saturday, October 16.
A spokesman said a lot of footage had been provided.
But, he said, detectives knew there were businesses in Carnarvon that were yet to offer up their footage.
Anyone else who was in the area at the time is also urged to hand over video footage to the police.