Cleo Smith went missing in WA's north. Photo / Facebook
The desperate search for Cleo Smith has led Australian police to scour through tonnes of rubbish in a bid to find any crucial evidence that could solve her mystery disappearance.
Cleo vanished from the family tent at the Quobba Blowholes campground, in Macleod near Carnarvon in Western Australia's north, on October 16.
Police said on Monday that they were leaving "no stone unturned", revealing officers had collected more than 50 cubic metres of rubbish from roadside bins as far north as Minilya and as far south as Geraldton.
"The rubbish was packed into two trucks and transported to Perth, where four forensics officers and 20 recruits spent two days sorting through hundreds of bags in an effort find any items that may assist in the investigation," police said in a statement.
Earlier on Monday, Police Commissioner Chris Dawson said his officers would never give up hope of finding the 4-year-old girl.
Asked whether time was becoming an enemy in the investigation, Dawson said police had gathered thousands of pieces of "really important information" as well as seizing thousands of forensic items.
"It's now been 16 days, and so clearly, every day that goes past is most difficult for Cleo's parents and loved ones," Dawson told reporters.
"Obviously, we share their concern. We'll continue to walk with them.
"Again, I appeal to the community, if you have any information, please bring it forward."
Mr Dawson promised police would never give up hope of finding Cleo alive.
"It's most important that we remain focused on the goal ... to find Cleo," he said.
"Obviously we're very, very concerned."
A major focus of the police investigation has been centred on a mystery vehicle seen by two people turning right off Blowholes Rd onto North West Coastal Hwy, heading towards Carnarvon, between 3am and 3.30am the day Cleo disappeared.
Police have repeatedly indicated the person may not be a suspect but may have relevant information.
Dawson confirmed on Monday that police were still yet to identify the driver of the vehicle.
As the investigation continues, police air wing officers will reportedly spend the next couple of days using drones to create a detailed map of the bushland area where Cleo was last seen.
In her latest heartbreaking social media post, Cleo's mother Ellie Smith again pleaded for information.
"Every day is getting harder without my shining bright light," she wrote on Instagram.
"Today, she's missed Halloween with her family — her cousins, aunties, uncles, nannas and pop — but most of all, her parents and baby sister.
"She needs us and we need her. She is loved, she is happy, she loves dressing up, whether it be a princess or a doctor. I just want her to come home.
"I need my baby girl home, please I beg you!"
Smith went on to urge anyone who spots someone acting suspicious to call police.
She also asked anyone who sighted Cleo, or had any important information, to call authorities.
A GoFundMe page created to support the search efforts and Cleo's family has raised more than $87,000 but organiser Bill Kent has now stopped taking donations.
"This has been a request made by Ellie and (Cleo's stepfather) Jake," he wrote on Monday.
"Thank you all so much for your kindness and generosity, and fingers crossed for some good news soon.
"Thank you to everyone who has been supportive in these times."
Police have repeatedly said Smith, Cleo's stepfather Jake Gliddon and her biological father Daniel Staines are not suspects in the case, but that has not stopped online trolls from saying vile things about them.
"They're going through a huge amount of angst and pain and suffering — they don't need this," Premier Mark McGowan told reporters on Sunday.
"I just don't get why some people get all this courage when they get a keyboard, and they say the most horrible and shocking things that they would never say otherwise.
"I just urge people to go back to a sense of decency and civility towards one another, particularly (towards) people who are suffering."
Lead investigator Detective Superintendent Rod Wilde has also repeatedly defended the parents.
Cleo was last seen about 1.30am on October 16 when she woke to ask for some water.
About 6am, when Smith and Gliddon woke up, they discovered Cleo and her sleeping bag were missing, prompting a large-scale search.
After there was no trace of Cleo, police said she was likely abducted, revealing a tent zip was opened to a height she could not have reached.
A desperate nationwide search has so far resulted in no suspects, despite police looking into paedophiles in the area and exploring other avenues of investigation.
A $1m reward has been offered by the state government for information that solves the girl's mystery disappearance.
Anyone with information is urged to contact Crime Stoppers.