Lillooet RCMP Sgt. Mike Eling said a 2005 Toyota Sequoia carrying a family of five crossed the centre line and side-swiped a northbound car with two occupants around 3:47 p.m.PT.
Eling said the collision sent the Toyota plummeting over a steep embankment down to the shores of the Fraser River. He said the 46-year-old driver and his two daughters aged 11 and four managed to get out of the car.
Rescue crews removed the two remaining passengers, a seven-year-old boy and a woman aged 46, who were pronounced dead at the scene, Elling said in a statement.
Police do not believe alcohol was a factor. However, Eling said the Lillooet area was experiencing heavy snowfall and police believe it was a contributing factor in the accident.