Friends are posting tributes to social media to remember a mother and her four children who died in a head-on collision involving a car and truck near Kingaroy, north-west of Brisbane.

Key points: Charmaine Harris McLeod and three of her children, aged under 10, died at the scene

Another child died while being flown to hospital

Police described the crash as an "absolute tragedy"

Queensland police said the crash happened when a Nissan station wagon being driven by Charmaine Harris McLeod tried to overtake a truck on the Bunya Highway at Kumbia, just before 7:30pm on Monday.

The car and oncoming truck collided before both vehicles burst into flames.

Ms McLeod, 35, from Eli Waters and three of her children, all aged under six, died at the scene.

Police said Charmaine Harris McLeod was trying to overtake a truck. ( Facebook )

Another child, a girl aged under 10, was taken to Kingaroy Hospital with life-threatening injuries.

She died while being flown to Queensland Children's Hospital.

One friend took to Facebook to say life would not be the same without them.

"Those kids were something else I tell you and lived like princes and princesses for their short life," Skye Moore said.

Two of the children, Aaleyn McLeod and Matilda McLeod, were students at Kawungan State School in Hervey Bay.

School principal Mark Jones said the community had been "deeply shocked and saddened by the death of two of our students".

"They were both joyful and friendly children who will be greatly missed by all their friends and teachers," he said.

"Our thoughts and sincere sympathies go out to the family, caregivers, friends and loved ones during this difficult time."

Mr Jones said support was being provided to students and staff.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 51 seconds 51 s Police have described the crash as an "absolute tragedy"

The truck driver escaped with non-life threatening injuries and is being treated in Kingaroy Hospital.

Assistant Commissioner Stephen Zsombok said paramedics were called to the "horrific scene".

"There were a number of people that were trapped and unable to escape from the fire that had engulfed the vehicle," he said.

"There was a lot of fire and smoke around the scene it was very difficult to get to."

He said someone at the scene was able to reach the young girl.

"Our officers ran through the smoke and fire to get to them, began working on them, and were able to treat and rapidly transport them to Kingaroy Hospital," Assistant Commissioner Zsombok said.

"The truck driver had burns to his arms and we believe that's actually from trying to help as well."

What remains at the scene of the crash on the Bunya Highway. ( ABC News )

Inspector Graeme Paine described it as an "absolute tragedy".

"This is a catastrophic incident scene. It's certainly one of the worst accidents that I've ever seen," he said.

"We will certainly offer whatever support we can to not only to the first responders on scene but also to the family.

"This is a tragic incident scene, the extent of devastation that will come from an incident like this not only for the family of the people involved but also the community."

Both vehicles burst into flames after colliding on the Bunya Highway. ( ABC News )

The Bunya Highway at Kumbia was closed for some hours on Tuesday morning.