Three feared dead in submerged NSW car

A mother and her two children are feared dead as police divers prepare to search for them in a car that was swept into a flooded northern NSW river.

Four people were in the car when it went into the Tweed River off Dulguigan Road in Tumbulgum on Monday afternoon.

A 10-year-old girl was able to escape the car as it was dragged into the water and residents at a nearby house came to her aid.

There are fears the other occupants, believed to be a female driver and her two children, may have perished with the car becoming fully submerged.

Witness Thomas Grinham saw the girl reporting her family members had been swept away by the floodwaters.

"She was screaming (that) her mum, little sister and older brother had gone into the river in the car," he told the Seven Network on Monday.

"Dad and two other boys just jumped into the water and couldn't dive deep enough," another young witness Sophie Grinham said.

Boats using sonar equipment found the car two hours later about five metres from the northern river bank.

The search operation will resume on Tuesday morning with police divers travelling up from Sydney.

A crime scene guard will remain at the scene overnight.

The child was taken to Tweed Heads Hospital for bruises and cuts and was being cared for by family members.

The northern NSW region has experienced record-breaking floods following last week's deluge.

Two women have been confirmed killed by the floodwaters which began rising on Friday.