The search was set to continue until police were able to completely rule out that there weren't other people in the auto.
On Wednesday, a passer-by came across the bodies of the 19-year-old couple and their son.
An air and land search was conducted Thursday to look for a 12-year-old boy who Nobbs said was believed to have been in the auto with the family.
A young family of three has been found dead next to a broken-down vehicle in a remote part of Australia's Northern Territory, according to police, who said a 12-year-old boy was still missing. Authorities initially thought the passengers had died in a vehicle crash but they now suspect the family died of exposure.
Five days earlier the group had left the remote indigenous community of Willowra with plans to travel to Warra Warra, 500 kilometers north of Alice Springs.
Remnants of food and water were found in the auto. Remnants of food and water were also found at the scene.More news: Trump's talk of Senate gain depends on undecided races
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Southern Desert Division Superintendent Jody Nobbs said police were yet to rule out that there may have been more passengers in the vehicle.
Superintendent Nobbs said the man who made the initial report to the health clinic in Wilowra would be interviewed.
"This is a tragic situation and our thoughts remain with the families affected by this incident".
NT Police were alerted to the deaths, which were not believed to be suspicious, when a person walked into a local health clinic and raised the alarm just after midday yesterday.
"This does serve, unfortunately, as a timely reminder for anyone travelling on NT roads to ensure that when you travel your vehicle is in a fit state, that you have sufficient supplies including water and a first-aid kit, and that someone is aware of what your travel itinerary is - when you intend to leave, arrive and your anticipated routes", he said.
Police urged anyone with information about the child's whereabouts to contact them immediately.