Detectives are inching closer to identifying every person in the area when Cleo Smith disappeared from a remote WA campsite, and they believe an opportunistic abductor snatched her.
Acting Police Commissioner Col Blanch told ABC Radio police were "getting closer and closer".
"And we've tracked down people that we didn't know, we've found them and we have eliminated them, and that's our focus at the moment — eliminate as many people as possible."
Police have also been searching the dark web for signs of the four-year-old, who vanished from her family's tent at the Blowholes campsite, about 80 kilometres north of Carnarvon, in the early hours of October 16.
She was not in the tent when her parents awoke at 6:30am, nor was her sleeping bag, and the tent's zipper had been undone to a height the little girl could not have reached.
A WA Police spokeswoman confirmed detectives were continuing to liaise with interstate and national law enforcement agencies who were helping with the investigation.
"Part of this has involved utilising their expertise and capability to investigate the dark web," she said.
Lead investigator Superintendent Rod Wilde told Nine Radio police had interviewed more than 110 people who were at the Blowholes campsite that night and believed there were only a "small handful" of people they had not yet tracked down.
"I think it's more than likely an opportunistic-type event," he said.
Police look for ground disturbance
Col Blanch said the forensic work on the ground involved creating a detailed map of every inch of the area, using drones, aircraft, and satellite technology to look for any disturbances in sand and other potential evidence.
"Now we're in a stage where we need to forensically go over that ground inch by inch to see what disturbances might be in nearby areas for any sort of evidence which might give an inkling as to what happened," Acting Commissioner Blanch said.
"It could be tyre tracks, it could be the sleeping bag, it could be anything."
He said police were in the process of securing satellite images captured over the area around that time, and were trawling through thousands of lines of data captured by mobile towers in the area.
"It is an investigative function for police to find out who was in the area at the time and perhaps the direction of movement — so what tower they started connecting to as they moved off."
Alternate escape routes investigated
While there has been focus placed on a mystery car seen turning off the Blowholes Road towards Carnarvon about 3:30am the morning Cleo Smith disappeared, other roads were also being investigated.
Acting Commissioner Col Blanch said there were many dirt roads and other routes which could have allowed an abductor to avoid detection.
"The Quobba Blowholes is a very remote area, you would need vehicles that are capable of doing that, you would be looking for a four-wheel-drive type vehicle," he said.
"But absolutely there are ways to go that aren't on the main road."
While police believe it is likely to have been an opportunistic abduction, Col Blanch said they were yet to rule out the possibility Cleo had been watched or followed at the campsite or even earlier.
"One of the most important things in an investigation like this is to eliminate everyone that was present at the campsite," he said.
"We need to know everyone who was there, and then we work out their movements, what they were doing, we take their DNA, their fingerprints, and that's all for elimination."
"We are left with a group of people that we would put more focus on."
Hard to keep up hope: police
The Acting Commissioner conceded that as time went on, keeping hopes high was not easy.
"It is difficult to keep the hope up, there is no doubt about it, the longer it goes, but I know those investigators are still focused absolutely on this case trying to bring Cleo home," he said.
"This has absolutely hit the heart of everyone in Western Australia, the Australian community, it's gone international.
"This is something we really want to solve, I look at my phone every morning hoping we've got an answer, it hasn't come yet, and I hope it does."
The Acting Commissioner also shed light on the make-up of the 100-officer Taskforce Rodia which is investigating Cleo's disappearance.
"We have nearly 50 officers up in Carnarvon, up at the Blowholes, working every day, and we have another 50 down in Perth," he said.
"And that ranges from detectives to analysts, forensic specialists, we're going to send the TRG up there to have a closer look and do some line searches, we've got drone pilots, we've got air wing.
"We basically have most of the police force specialist services and detectives working on it."
Cleo's family 'had quiet night'
Detective Superintendent Wilde revealed that on the night the family arrived at the campsite, they did not have any direct interactions with other campers.
"They had a quiet night around the campfire and that was it," he said.
"We know they got there on the Friday night, and it was getting dark, so there would have been limited opportunity for someone to observe Cleo at that time."
He also said video on either Ellie Smith's or Jake Gliddon's phone corroborated the fact Cleo was at the campsite on the night in question.
"We've got some evidence off the parents' phone, which obviously we can geolocate and all of those types of things, which puts them at that location, at that time, with footage of Cleo on it," he said.
Superintendent Wilde said police dogs had not been deployed at the site, but they could be used at a future date.
