Mountains of rubbish have been collected from roadside bins as far south as Geraldton, more than 500 kilometres from where she vanished, and as far north as Minilya, 165 kilometres away.
The rubbish was packed into two trucks and transported to Perth, where four forensics officials and 20 officers have spent two days sorting through hundreds of bags in an effort to find any items that may offer clues.
WA Police Commissioner Chris Dawson said officers were not giving up.
“We’ve got thousands of (pieces of) really important information plus of course the thousands of forensic items we’ve seized, but it’s now been 16 days,” he said.
“Every day that goes past is most difficult for Cleo’s parents and loved ones, obviously we share their concern.
‘We never give up hope and it’s most important that we remain focussed on the goal and the goal is clearly to find Cleo.”
Cleo’s mother, Ellie Smith, posted another plea on social media.
“Every day is getting harder without my shining bright light,” she said.
“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 is loved, she is happy, she loves dressing up whether it be a princess or a doctor.
“I need my baby girl home, please I beg you!”
Detectives were also at the Carnarvon harbour, still tracking down everyone who was near the Blowholes campsite where Cleo disappeared from a tent.
Drone operators are mapping a 50 kilometre radius of the remote area.
But still a mystery is whoever drove a car south from Blowholes Road around the time Cleo disappeared.
Having raised almost $90,000, a fundraising page set up by a family friend has now been closed at the request of Cleo’s parents.
The money will help pay for the helicopters and search teams, with any leftover going to Ellie and Jake, who have thanked the community for their generosity.