A mother has been charged with murder two days after members of the public found her and three children stabbed in a car.

The passersby came across the vehicle on the side of a road in the Blue Mountains, west of Sydney, about midday on Sunday and gave first aid.

Emergency services later found a five-year-old child had died and provided treatment to two other children aged one and three and to the 42-year-old woman.

They were taken to Westmead and Westmead Children’s hospitals. The children are still listed as critical.

Detectives on Tuesday charged the woman in a bedside court hearing with murder — domestic violence along with two counts of wounding with intent to murder — domestic violence.

She was denied bail to appear before Penrith Local Court in November.

Local Superintendent John Nelson on Sunday said the father was “going about [his] business” at work when he received news of the alleged attack.

“You can imagine receiving that tragic news,” he said at the time.

The woman was not previously known to police, Nelson said.

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Men’s Referral Service 1300 766 491

-AAP