Four-year-old Cleo Smith found seven minutes from family home

Four-year-old girl Cleo Smith, who went missing from a remote campsite in Western Australia, has miraculously been found alive after 18 days of searching.

But in a heartbreaking turn of events, she was found in a locked house just seven minutes from her family home in Carnarvon.

Police broke into a locked house in Tonkin Cres in the early hours of Wednesday morning where they found Cleo alone, but alive.

A leading criminologist said finding Cleo alive was a "miracle" and "highly unusual".

"I had been expecting the worst," Dr Xanthe Mallett told Sunrise just hours after Cleo was found at a home in Carnarvon in Western Australia.

Cleo Smith has been found alive and well. Photo / Facebook

"It is highly unusual to find an abducted child alive and well after so long. This is a miracle."

Cleo went missing from a remote campsite in WA 18 days ago, sparking a wide-scale search and fears she had been abducted.

WA Police Deputy Commissioner Col Blanch released a statement on Wednesday morning announcing the extraordinary development.

He also revealed "phone data" helped lead police to the house where Cleo was found.

"It will become apparent when we put the puzzle together … it all led us to one place," he said.

"A police team broke their way into a locked house in Carnarvon about 1am. They found little Cleo in one of the rooms.

"One of the officers picked her up into his arms and asked her 'what's your name?'

"She said, 'My name is Cleo'. Cleo was reunited with her parents a short time later."

A 36-year-old man from Carnarvon is in custody and being questioned by detectives.

Police sift through rubbish for clues. Photo / WA Police

Dr Mallett said she wasn't completely surprised that there was finally a conclusion to the case that had baffled detectives for almost three weeks.

"Strategically, police seemed to be clear on where they were going," she said.

"I am just incredibly pleased it is a positive outcome."

She was then asked about the vehicle that was spotted leaving the carpark of the campsite just hours after Cleo was last seen by her parents.

Police said it was likely she was abducted in the dead of the night since the tent zip was opened to a height she could not have reached.

A major focus of the police investigation has a mystery vehicle that was spotted by two people.

They said it turned right off Blowholes Rd onto North West Coastal Highway, heading towards Carnarvon, between 3am and 3.30am the day Cleo disappeared.

"It may be that car that was the key to solving this … it may have been something else," Dr Mallett said.

"They have looked closely in the local community. We always felt this was something targeted. To me, it made no sense this was a random.

Cleo Smith was missing for almost three weeks. Photo / Facebook

"They have looked very closely at those in the community, those who possibly know Cleo. There will be a link to Cleo and her family. Over the next day or so, will find more about what has happened."

Search crews combed the coastline near the remote camping ground where Cleo went missing, but efforts proved futile.

Police also examined CCTV footage from businesses and homes that might have captured the car or anything else that might be relevant to the investigation.

They then moved search efforts to Cleo's parents home, which they searched three times. Police said her parents were not suspects and the move was "standard practice".

Officers searched the home for several hours before leaving with two evidence bags.

A 36-year-old man is now in custody and being questioned by police after Cleo was found at his home in Carnarvon.

WA Police Commissioner Chris Dawson said the man had no connection to the family.