Police are continuing to investigate a fatal crash that killed two children at a south-east Queensland dam about 2pm on Sunday.

Queensland police said two adults and four children were in a LandRover Discovery when it broke through a road barrier, rolled down an embankment and ended up on its roof in water at Wyaralong dam, near Beaudesert, south-west of Brisbane.

Inspector Doug McDonald said the adults – a man, 23, and a woman, 33 – were able to get out of the vehicle.

Passers-by, including two doctors and an off-duty paramedic, helped them pull the children from the vehicle. But a four-year-old girl and a 13-year-old boy were trapped for some time and could not be revived.

A one-year-old boy was flown to hospital after the crash.

Having initially been listed as critical, he was in a stable condition in hospital on Monday.

A five-week-old baby girl was treated at the scene. She is in a stable condition in Brisbane’s Children’s Hospital.

The man and the woman were taken to hospital with leg injuries. They are expected to have surgery on Monday.

The injured were flown to hospital in Brisbane. Photo: ABC

Police have confirmed the family were from Pratten in Queensland’s Southern Downs and the adults are a couple. They were travelling to somewhere near Warwick when the accident happened.

Investigators do not believe alcohol was a factor in the horror crash. Early indications are that those in the vehicle were all wearing seatbelts.

“Certainly I can say that in these types of instances, where we have high-speed rollovers, seatbelt save lives, there is no doubt about it,” Inspector McDonald said.

He said the LandRover appeared to have veered left on a straight section of road above the dam. It struck a three-strand wire barrier before crossing to the other side of the road and colliding with another road barrier.

“The vehicle subsequently rolled down a stone embankment and came to rest on its roof in semi-submerged position in the dam,” he said.

Police divers and forensic teams spent the night at the site and the car was removed from the water.

Inspector McDonald said the accident scene was traumatic for all involved.

“It is really traumatic for our first responders and also for members of the public that stopped and did a fantastic job out there,” he said.

A Queensland Police officer was also injured when his vehicle rolled as he was rushing to the scene on Sunday.

“Thankfully, he was wearing a seatbelt, as he should, and has relatively minor injuries considering the vehicle rolled and ended up on its roof on the way to this job,” Inspector McDonald said.

The Beaudesert-Boonah Road was closed for most of Sunday night.

Several people will be interviewed in coming days.

-with agencies