The search for Cleo Smith has entered its third day. She was last seen about 1.30am on Saturday at the Blowholes campsite on the coast at Macleod, north of Carnarvon.

The girl was wearing a pink one-piece sleepsuit with a blue and yellow pattern.

Amid speculation she either wandered away from the campsite or had possibly been abducted, Commissioner Dawson said the environment in the region was very tough and it was a "very unusual situation where we don't where Cleo is".

"Police are not ruling anything in or out. Police are conducting an extensive search of the area," he told reporters on Monday.

"We've brought in forensic trained investigators from our homicide and major crime divisions as well.

"We're keeping all avenues open. We just want any information concerning Cleo."

On Sunday, the girl's worried mother, Ellie Smith, took to social media also pleading for help.

"It's been over 24 hours since I last seen the sparkle in my little girl's eyes! Please help me find her," she posted.

Earlier, Ms Smith posted that she had woken at 6am on Saturday to find her daughter wasn't in their shared tent.

She described Cleo's disappearance as "very, very unusual".

Police said previously they were"fairly confident" they had been able to get the identities of all the people who were in the campsite at the girl disappeared, as well as gathering intelligence from dashcams and CCTV cameras in the vicinity.

Deputy Premier Roger Cook said Cleo's family was going through "immeasurable pain".

"All Western Australians' hearts go out to them," he said.

Australian Associated Press