SYDNEY — A four-year-old Australian girl was found "alive and well" on Wednesday (Nov 3), police said, sparking elation Down Under more than two weeks after she disappeared from her family's tent during a camping trip.

Cleo Smith was found after police forced their way into a locked house in the coastal town of Carnarvon, not far from where she was last seen 18 days ago, Western Australia police said in a statement posted to Facebook.

"One of the officers picked her up into his arms and asked her 'what's your name?'," police deputy commissioner Col Blanch said in the statement.

"She said - 'My name is Cleo'."

Police detained a man from Carnarvon for questioning after breaking into the house at about 1:00 am (1 am, Singapore time) local time, Mr Blanch said.

The young girl was reunited with her parents a short time later, with her mother Ellie taking to social media to express her relief.

"Our family is whole again," she posted on Instagram under a photo of Cleo.

The reunion came after an extensive air, sea and ground search that drew national attention, with many Australians taking to social media to express their joy after more than two weeks of anguish.

"This is the outcome we all hoped and prayed for," Mr Blanch said.

Western Australia police commissioner Chris Dawson said officers were questioning a 36-year-old man who had no connection to the girl's family.

No further details were released about the exact circumstances of her disappearance or how she was tracked down.

Investigators were determined they "were not going to leave any stone unturned", even as the search dragged on, Mr Dawson said.

"We had been following a lot of the forensic leads and it led us to a particular house," he told ABC radio. "We put everything we had at it."

"Hope was never lost and the fact she's been found alive, I think Australia is rejoicing. It is such a wonderful outcome."

Police last month had offered A$1 million (S$1 million) for information leading to Cleo's recovery after she was feared abducted from her family's tent at the remote Blowholes campsite — about 1,000 kilometres north of Perth — on Oct 16.

Detective Superintendent Rod Wilde said at the time that the investigation "leads us to believe that she was taken from the tent", and that authorities had reason to fear for her safety.

Ms Ellie Smith had described her distress at waking at 6.00 am to find the tent unzipped and her oldest daughter missing and had issued public pleas for help to bring her home.

Police on Wednesday praised the family for their strength through the ordeal, while thanking the local community and volunteers for their help in the search. AFP