The four-year-old is thought to have been abducted from a tent while camping with her family at the site north of Carnarvon.
Forensic investigators were collecting soil samples from a number of campfires near the shacks in the area, on Wednesday.
The officers have also gone back to the family’s home in Carnarvon, following initial searches on Tuesday.
Acting Police Commissioner Col Blanch said Cleo's parents had been cooperative.
"I must be very clear so that people don't make assumptions on this. That is standard practice in any investigation," he said.
"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 the investigation and we must follow it through thoroughly."
Detective Superintendent Rod Wilde is heading up the 100-person-strong Taskforce Rodia and is due to fly into Carnarvon on Thursday morning.