A child's decision to sleep with her parents because of an upset stomach on the night of a fatal house fire in northern British Columbia may have saved her life.

The fire that ripped through a two-storey home in Mackenzie, B.C., early Tuesday killed two infants just weeks shy of their second birthdays.

Gabrielle and Joseph, twins, were sleeping in their bedroom on the home's upper floor when the fire broke out.

But their three-year-old sister Kate-Lynn, who often slept upstairs, survived after heading downstairs to spend the night.

"It definitely saved her life that she was downstairs," grandmother Debra Baxter told CTV British Columbia.

"The only window left in that house is their bedroom window in the basement."

Five members of the family were inside the home at the time of the fire, which broke out about 7:30 a.m. in the small community, which is about two hours north of Prince George.

When fire crews arrived only minutes after the fire was reported, the home was totally engulfed in flames.

Along with firefighters and emergency crews, the children's parents -- Lanora Baxter and Rick Fleury -- tried to get inside the home to save the twins.

However, the flames were too much.

The survivors were treated for injuries at the Mackenzie District Hospital, RCMP Const. Lesley Smith said Tuesday. They have since been released.

Baxter said she was devastated by the news that her grandkids had died. She said that comforting her granddaughter has also been difficult.

"She said ‘Daddy okay, Daddy okay?' And then she looked at me and said ‘Gabby and Joey not okay.'"

CTV B.C. reporter Kent Molgat reported that the tight-knit community is showing support for the family's loss and was visiting the grandmother's home.

"Certainly this family is going to have lots of support as they cope with this tragedy," he said.

Molgat said the twins were found in their beds, giving the family hope that they did not suffer pain before their deaths.

The cause of the fire isn't yet known.