Two children have been killed in a single-vehicle crash at Peak Crossing, south-west of Brisbane.
Another child and a woman in her 30s were also seriously injured in the accident.
The woman has been airlifted to hospital in a critical condition, while the child has been taken to the Queensland Children's Hospital in a serious condition.
Paramedics were called to the scene on a straight stretch of Middle Road about 2:45pm.
The ABC understands that police were in the vicinity conducting a traffic operation when they discovered the car was registered to a learner driver, and had endeavoured to intercept the vehicle prior to the crash.
Police said there was no pursuit and officers were not near the vehicle when it crashed and could not confirm whether speed was involved.
The Forensic Crash Unit is being overseen by the Ethical Standards Command in investigating the incident.
It will include reviewing body-worn camera and dash cam footage.
Meanwhile, a crash involving multiple cars and a bus has been causing traffic chaos at Jindalee in Brisbane's west.
Initial reports from the scene suggested 20 vehicles were involved in the pile-up, but police later said it was six cars and a bus.
Five people were taken to hospital from the Jindalee crash scene, with a total of 27 people assessed at the scene by paramedics.
Emergency services were called to the crash on the Centenary Highway about 2:15pm, as heavy rain, strong wind and hail hit parts of the region.
Police and the Brisbane City Council urged drivers to avoid the Centenary where possible.
Deputy Mayor Adrian Schrinner said authorities were still assessing the incident.
"There were multiple vehicles involved including a council bus," he said.
"I understand there was a car in front of the bus which stopped suddenly.
"The bus crashed into the car and then many more cars crashed into that bus. So that's the early report that I've had."
