The crash that killed a QLD mother and her 4 kids may not have been an accident, police say.

Almost a week after the car crash that killed a Queensland mother and her four young children, Queensland homicide detectives are investigating the possibility the accident may have been deliberate.

Charmaine Harris McLeod, 35, and her children Aaleyn, 6, Matilda, 5, Wyatt, 4, and Zaidok, 2, died after their station wagon slammed into an oncoming truck south of Kingaroy on Monday night.

Police are now looking at whether the crash was a murder-suicide, after a note believed to have been handwritten by Ms McLeod was found approximately 200 metres away from the scene by investigators, The Courier Mail reports.

This evidence, along with an absence of skid marks at the scene that suggest Ms McLeod hadn’t tried to stop the car, has resulted in homicide investigators and other specialist police being asked to assist in the investigation.

Queensland Police Commissioner Ian Stewart said on Friday they have not yet added the deaths of Ms McLeod and her four children to the official road toll because there is a possibility the crash was not an accident.

On Monday, paramedics had to fight their way through flames and smoke to reach the vehicle, which was set ablaze along with the truck on Bunya Highway, just south of Kingaroy.

They managed to pull out one of the girls who’d suffered horrific burns, but there was nothing they could do to save the others who died there.

The girl who was pulled from the car made it to hospital but died while on a rescue flight bound for Brisbane. The truck driver was injured but managed to free himself as the blaze spread to surrounding grass.

Police initially believed the children’s mum was trying to overtake when her car slammed head-on into the truck, which was travelling in the opposite direction. They were calling on Wednesday for any witnesses who might have seen the accident or have dashcam footage to help them piece together exactly what happened.

Police are also looking into Ms McLeod's online activity for any clues as to why the mother-of-four was driving three hours away from her Hervey Bay home where the crash took place, when there were no relatives in the area or nearby.

Weeks before she died, Ms McLeod posted a message about feeling alone on Facebook.

“I feel as if, if you cant or don't grasp God/healing etc, when they think you should have then you just get left behind,” she wrote on the page for her local church last month.

“You would think there would be support/help, but very very little, they were always too busy, not one piece of clothing or a piece of bread was offered, let alone shelter.

“I feel as if I’ve done it alone… these are the things Jesus did, he ate with the less fortunate.. I’ve asked for prayer before surgery & yes I’ve had a lot of surgeries but they don’t, they do for others though.”

The children’s distraught father James McLeod has described his last visit with the beautiful souls, who he says were loved by everyone who knew them.

He told the Courier Mail on Wednesday it was during this last visit that his youngest son, Zaidok, told him he loved him for the first time.

“Young Zaidok – he was just a little adventurer. A loving and kind kid,” McLeod told the newspaper.

“The last supervised visitation I had with them, not last Saturday but the Saturday beforehand, he actually said that he loves me, daddy, to me. Just out of the blue.

“They were beautiful, intelligent, bright, smart kids.”

Bayside Christian Church assistant pastor Peter Ford, who first met Ms McLeod when she was a teenager in Hervey Bay, remembers her as an active church member and the driving force behind a decade-old community barbecue event on Christmas Day for people without family and friends.

“In her younger days, she also worked with Youth In Search, which is a Queensland-wide organisation,” he told AAP.

“She really wanted to help others and the community – she had a heart for that.”

A GoFundMe in honour of Ms McLeod and her children has so far raised over $17,000.

- With AAP.

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