RCMP say the family of five was returning home to Coaldale when their vehicle left the roadway on a straight stretch around 2:30 p.m. MST.
Police say it appears the driver lost control of the van in the slushy centre of the highway while attempting to pass another vehicle.
The white Chevrolet minivan came to rest upside down in the river. A passing motorist and his girlfriend climbed down into the the river and pulled all five occupants from the minivan, said police.
Police and bystanders attempted to save the woman with CPR but she was pronounced dead at Fernie Hospital. But RCMP and a doctor who happened to be at the accident scene did manage to save a four-year-old child with CPR.
Two of the children were transported by air ambulance to Alberta Children's Hospital with severe injuries. The male driver and one other child were treated at Sparwood Hospital in B.C. for minor injuries including hypothermia.
The Fernie man who helped pull the family from the submerged vehicle was also treated for hypothermia and released.
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