A Kiwi mother who died in a river tragedy was found "holding a child" in the submerged vehicle, police say.

New Zealander Stephanie King, 43, of Bilambil, died trying to save her children 7-year-old son Jacob and her 11-year-old daughter Ella-Jane after their car careered off the road into the flooded Tweed River yesterday.

Tweed Byron LAC Chief Inspector Mick Dempsey told News Corp King was found "holding a child".

Read more: Kiwi mum and children in Tweed River tragedy

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Superintendent Wayne Starling described King as "a hero (who) died trying to save her children".

"I have no doubt she would still be alive if she wasn't trying to save her children," he said.

Asked about how 8-year-old Chloe managed to escape the sunken vehicle and run for help, Dempsey suggested King helped her escape.

Police confirmed the bodies of the three were found in a submerged vehicle, about 5m from the riverbank.

The mother and children have been remembered as a "perfect normal family", by devastated friends.

The close-knit northern NSW community has already reached out to support King's partner, Matt Kabealo, a chef at the Kingscliff Bowling Club.

Devastated friends have expressed their shock on social media. One wrote: "It makes me sick knowing a beautiful family is still in the water, such a precious loss to all that knew you, I know I will miss you terribly".

Jacob and Chloe May King. Jacob, along with another sister Ella Jane, died when the car the family were travelling in was washed away. Chloe survived the accident. Photo / Facebook
Jacob and Chloe May King. Jacob, along with another sister Ella Jane, died when the car the family were travelling in was washed away. Chloe survived the accident. Photo / Facebook

One neighbour, Steven Moller, told News Corp he saw King just the other day.

"They were a perfectly normal family, I would see her loading her kids into the car," he said.

New Zealand-born King worked as an assistant in nursing at Opal Aged Care in Tweed Heads and previously was employed at the Tweed Heads Bowls Club, according to her Facebook profile.

Former police officer Matthew Grinham was driving by flood waters at Tumbulgum on Monday afternoon when he saw a girl hysterically screaming while running along the road, yelling that her mum, little sister and brother were trapped in the river in the car.

"We pulled up just after the car went under," Grinham recalled, speaking with the Daily Telegraph. "She couldn't say much, she just said my mum, my little sister and my [older] brother have gone in the river in a car."

Grinham told reporters he initially thought a calf had fallen in the water, but realised the situation was dire and leapt to action.

"I looked down on the road and saw the skid marks of a car, its tracks were in the mud and I just jumped in," he told The Australian.

Police divers recover one of three bodies from the submerged car in the Tweed River. Photo / News Corp
Police divers recover one of three bodies from the submerged car in the Tweed River. Photo / News Corp

The Tumbulgum local described the freezing and "horrible" murky flood waters, and the sense of despair he felt when he realised he wouldn't be able to retrieve the car and the family members it was carrying.

"The helplessness of not being able to find the car, the bubbles were there, we could find the bubbles, we just couldn't get to the car," he said.

"At first we were going to go feet first, just pushing down to try and see if we could feel it with our feet. I tried a couple of times, but the bubbles, they trailed away. They just got less and less."

The girl who managed to escape and raised the alarm with nearby farmers and passers-by like Grinham, was taken to hospital with minor injuries and is being cared for by family members.

Nine News reported the children's father was "beside himself".

NSW Police Assistant Commissioner Jeff Loy said the tragedy would have a "major impact" on not only the family, but the wider Tweed community.

Police will also investigate how the woman came to be driving on the closed road by the river's burst banks.

The tragedy is the latest in what's been a devastating few days for flood-hit northern NSW residents, with two women aged 36 and 64 confirmed dead and a man dying of a heart attack.

A massive clean-up operation is under way as communities pick up the pieces of ruined homes and businesses. Damage is widespread along the east coast and further inland where ex-tropical Cyclone Debbie has caused flooding and destruction since early last week.

In Queensland, Rockhampton is still bracing for the worst of the cyclone's after-effects.

Lismore, Murwillumbah and Tweed Heads residents have been given he all-clear to return home after floodwaters washed through the region over the past three days.

NSW Premier Gladys Berejiklian and Prime Minister Malcolm Turnbull visited flood-hit communities on Monday to reassure locals they'd be given support.