The family was returning to Sydney after visiting Thredbo when their silver Chrysler Voyager rolled about 5km north-west of Berridale on the Kosciuszko Road.

Five children aged between four and 13 and their 40-year-old mother suffered relatively minor injuries.

The father, who was driving the car, and believed to be aged in his 40s, died at the accident scene near the Eucumbene Dam turn-off. It is believed he was being tended to by his wife when he died at the roadside.

The car rolled several times before landing on its wheels.

It is understood the family of seven had spent the weekend at the snow with two other families.

The three families were making their way back in convoy when the Chrysler rolled at about 2.30pm yesterday.

Four ambulances, police and Snowy Hydro SouthCare were called to the scene a short time later, with the man trapped in the vehicle suffering severe head injuries.

Paramedics from Jindabyne and Cooma took the mother and five children to Cooma Hospital.

A four-year-old and 13-year-old were flown by the Snowy Hydro Southcare helicopter to Canberra Hospital to be treated for injuries.

They were initially listed in a serious condition, but their condition improved late last night and were listed as stable.

The three other children and mother were driven to Canberra Hospital, with the 40-year-old woman requiring treatment.

Traffic was banked up as police closed off Kosciuszko Road for about an hour while rescue crews worked to remove the wreckage of the seven-seater van.

Late last night NSW Police said the cause of the crash was still unknown, with the investigation to continue.

Police are calling for any witnesses to call Crime Stoppers on 1800333000.

A report will be prepared by investigating officers for the NSW Coroner.

The names and suburb of the family involved had not been issued last night.

- with Sonia Byrnes