Two adults, both aged 19, and their three-year-old son have been found dead after their car broke down on a remote road in the Australian outback.

Police said the bodies were found 4.5km from the vehicle, around 1,000km (620 miles) south of Darwin on Wednesday.

Northern Territory Police said a search was also underway for a 12-year-old boy who was believed to be a passenger in the car.

The deaths are not being treated as suspicious.

Authorities are investigating whether heat may have been a factor in their deaths as temperatures had reached 40C in the area over recent days.

The group was last seen on Friday leaving Willowra, a small settlement 210 miles north of Alice Springs.

Police were alerted to the deaths when a man entered a local health clinic and raised the alarm just after midday on Wednesday, ABC News reports.

They did not say who had alerted authorities, but police believe he will be crucial to the investigation, and was “quite distraught from what he’s found.”

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Northern Territory Police Superindendent Jody Nobbs said: “Initially we thought it was the result of a car crash, however we’re confident it’s not.

“We don’t believe the circumstances are suspicious.”

Police said they would continue investigations and prepare a report for the coroner.

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They also warned about the dangers of travelling through remote areas of the country.

“This does serve as a timely reminder to anybody travelling on the Northern Territory roads, when you do travel, your vehicle is in a fit state for travel,” Superintendent Nobbs said.