A NINE-year-old Nambour boy has died after being flung 18m from a car during a crash near Gladstone early Tuesday morning.
A four-year-old boy, believed to be the nine-year-old's brother, was also flung from the wreckage.
He is in a critical condition at Brisbane's Royal Children's Hospital with serious head and spinal injuries.
Four others - three children and the 36-year-old female driver - are in a stable condition at Gladstone Hospital.
The devastating Bruce Hwy accident rocked dozens of local emergency services workers who raced to the scene.
The children attended Nambour's Flametree Baptist Church, and senior pastor Joel Baker said the church community was still trying to comprehend the tragic loss.
"We all grieve with the mother and are praying for the recovery of the little one," he said.
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The crash happened along a stretch of the Bruce Highway at Bororen, 50km south of Gladstone.
Six occupants were in a late model Toyota Prado when the 4WD veered across to the other side of the road and rolled down a steep embankment about 12.30am.
The nine-year-old boy was thrown from the car and was deceased when found, while the four-year-old boy was airlifted to Brisbane's Royal Children's Hospital after suffering critical head and spinal injuries.
Accident investigation officers were on scene, but Miriam Vale's Sergeant Owen Harms said initial indications were that fatigue could have contributed to the accident.
"We believe fatigue could be a contributing factor to the crash, and if so it clearly displays a message that adequate breaks while driving are absolutely necessary," he said.
Sgt Harms said the occupants were south-bound on a reasonably good stretch of highway when the crash occurred.
"(The 4WD) tragically left the road, went down a steep embankment and overturned, during which some of the juveniles were thrown from the car," Sgt Harms said.
One child was trapped in the vehicle before being airlifted to Brisbane, while two children were also thrown from the Prado.
The nine-year-old who died at the scene was thrown up to 18m from the car, while the other child was found in a nearby tree.
Sgt Harms said the accident had affected responding emergency services officers.
"It's just so tragic when a young kid gets killed. It's particularly emotional and it definitely impacts on emergency services that have to attend these scenes," he said.
The 4WD will undergo a police mechanical check as investigations into the crash continue and local police plead for people to take adequate breaks.
Investigations are continuing. Anyone with information should contact Crime Stoppers on 1800 333 000.