A family camping trip involving two young children and their grandparents has ended in tragedy after the motorhome they were sleeping in caught fire overnight in B.C.'s Fraser Canyon.

Police say the grandparents, who are both in their mid-50s, were asleep in the rear of the motorhome when they were awoken by the RV's smoke alarms and their two dogs.

The couple was able to reach the two youngsters, a four-year-old boy and five-year-old girl, who were sleeping in the front right-side pull out.

The pair carried the children to the back of the vehicle, and then the grandfather told his partner to push each child out of the rear-side window once he climbed out.

Once the children were out, police say the woman collapsed inside. She was rescued by two other people, employees of her partner, who were camping nearby.

The employees smashed a window of the motorhome to get inside and rescue the grandmother.

Police say the children were breathing when they were removed from the vehicle, but later succumbed to their injuries in hospital. Their names have not been released.

The grandparents remain in hospital in Kamloops. Their two dogs perished in the fire.

The 35-foot 2006 motorhome was parked at a decommissioned air strip off Highway 1 about two kilometres north of Lytton when the blaze erupted in the front area of the vehicle shortly before midnight Wednesday.

Mounties, ambulance paramedics and volunteer firefighters from Lytton attended the scene, providing first aid to all four occupants before transporting them to hospital.

Police have notified the children's mother and father, who live separately in Armstrong and Surrey, and Victim Assistance personnel will be providing them support.

Chris Pieper, mayor of Armstong, said he doesn't know the family but his wife works at the elementary school where the girl attended classes.

"I know there was grief counselling brought into the school first thing this morning and the school had people, all day, dealing with issues at the school," said Pieper.

He said the four-year-old boy also attended an Armstrong preschool.

The school, Highland Park Elementary, did not issuing any formal statements out of respect for the family.

The BC Coroners Service and Office of the Fire Commissioner are examining the fire scene, but have not yet determined the cause.

The blaze, which started in the driver's area, is not considered suspicious.