Search for missing WA girl Cleo Smith continues after she vanished from campsite

WA Police said Cleo's family woke to find her missing about 6am, having last seen her inside the family's tent about 1.30am that morning. Photo / Supplied

Homicide detectives have reportedly joined the third day of searching for a young girl who vanished from a campsite in Western Australia's remote northwest on Saturday, as "gravely concerned" police are not ruling out she could have been abducted.

Four-year-old Cleo Smith was staying with her family at the Blowholes campsite in Macleod when she was reported missing on Saturday morning.

WA Police said Cleo's family woke to find her missing about 6am, having last seen her inside the family's tent about 1.30am that morning.

The West Australian reported on Monday that homicide detectives had now joined the search and investigation efforts.

Her mother Ellie Smith took to social media to urge anyone who might have seen her "sparkling" Cleo to call police, saying she was wearing a bright pink suit before she vanished.

The seaside campsite is located about 75km from Carnarvon and 875km north of Perth.

Police and the State Emergency Service launched an extensive land, air and sea search but found no trace of Cleo after two days of investigations.

On Sunday, WA Police Inspector Jon Munday said the force was "throwing everything we can at this search".

Inspector Munday said the circumstances around Cleo's disappearance were "unusual" and "extremely concerning" and confirmed a sleeping bag had also been reported missing.

"We are gravely concerned for the safety of Cleo," he said.

"We are not leaving anything to chance. We are trying to cover all our bases and we are not ruling anything out. So we are going as hard as we can, as long as we can, to try and find Cleo."

Police worked to ascertain who was staying at the campsite at the time of Cleo's disappearance and had searched campers leaving the site.

The "extremely harsh" environment surrounding the site was of concern if she did wander off, Inspector Munday said, but conditions at the time were conducive for survival.