UPDATE: A Queensland Police spokeswoman said the death of a three-year-old boy in Tinana is believed to be non-suspicious but investigations are continuing.
Police media could not confirm whether an autopsy on the child is being performed today in Brisbane, as reported by the ABC.
The cause of death is still unknown.
EARLIER UPDATE: A three-year-old boy died in Maryborough Hospital after being found in a car in the backyard of a Tinana home on Tuesday.
Wide Bay Burnett district Detective Inspector Bruce McNab said it was too early to tell the cause of death and investigations were continuing.
He said the death had not been ruled as suspicious at this stage.
"Both parents are very, very distraught," he said.
Det Insp McNab said police were doing further testing on the car and interviewing the parents, neighbours and ambulance officers who attended the scene.
He said police had been called to the property about 3pm on Tuesday and would continue to work at the property on Wednesday.
EARLIER: Police are investigating the sudden death of a child at a Tinana home.
Late on Tuesday afternoon, emergency service crews surrounded a property on the corner of Uhlmann St and Woongool Rd in Tinana.
Detective Sgt Melonie Geck from the Maryborough Police District Child Protection and Investigation Unit, along with local police officers, ambulance and forensic investigators were on site.
About 5pm, the home was taped off and police were asking people to move along as they examined the area.
At 6pm on Tuesday, it was not known whether the death was being treated as suspicious.
The age of the child is not known.