The family of missing four-year-old Cleo Smith has made a desperate appeal to the Western Australian public for information as a police search enters its fifth day.

It came as it was revealed police were also probing reports a car had been heard speeding from the popular Blowholes site, on WA’s north-west coast, early on Saturday morning.

Cleo was last seen by her parents about 1.30am on Saturday in the family’s tent at the remote campsite, about 900 kilometres north of Perth.

The girl was wearing a pink one-piece sleepsuit with a blue and yellow pattern. Her red and black sleeping bag is also missing.

Homicide detectives are assisting local police amid fears Cleo may have been abducted – although they say they have not given up hope of finding the little girl in the area.

“To say we’re treating this as an abduction is not correct,” Assistant Commissioner Darryl Gaunt told Perth radio 6PR on Wednesday.

“We’re treating it as a search and rescue mission, first and foremost, and that remains our mission.”

In an emotional interview, Cleo’s mother Ellie Smith said the little girl would never wander off on her own and someone must know where she was.

“She would never leave us, she would never leave the tent,” she said.

“We hold hope that she’s here [near the campsite] because if I think about her being taken … a million other things cross our mind.

“We sit and watch the sand dunes and we just think she’s going to run down it and back into our arms but we’re still waiting.”

Ms Smith said she and her partner Jake Gliddon had woken about 6am on Saturday to Cleo’s baby sister Isla wanting a bottle.

When she went into the other room, Cleo was gone and the tent was “completely open”.

Authorities were on Tuesday forced to temporarily suspend the land search due to damaging gusts and heavy rain in the Carnarvon area.

The search resumed hours later, with mounted police deployed to join a search that also includes SES volunteers, a helicopter and drones.

Police have already searched all of the shacks along the coastline at the campsite but will revisit some for a further look.

Other campers have reported hearing screeching tyres early on Saturday.

“As time goes on, we know the forecast going forward gets worse each day,” Mr Gaunt said.

“It’s every parent’s worst nightmare.”

Detectives have also spoken to Cleo’s biological father in Mandurah, south of Perth, as part of their investigations.

There is no suggestion he was involved in the girl’s disappearance.

Ms Smith said it had been a horrendous ordeal for the family, describing Cleo as a beautiful and delicate girl with “the biggest heart”.

Ms Smith said it had been a horrendous ordeal for the family, describing Cleo as a beautiful and delicate girl with “the biggest heart”.

-AAP