Around 7 p.m. Sunday, the fire completely engulfed the home in Sicamous in the south-central part of the province.
It killed a 28-year-old man identified only as Daniel and his two sons. His fiancee and mother of the boys, Kara Wagner, 25, was working down the street when she heard news of the fire, The (Vancouver) Province reported.
Royal Canadian Mounted Police spokesman Constable Thomas Blankey said an investigation was under way Tuesday, but "we're not sure of the cause of the fire [though] we believe the fire is not of a criminal nature."
Fire Chief Brett Ogino said the fire was so intense, it took 20 minutes to put out.
An unidentified neighbor told The Province the fire seemed to suddenly completely consume the mobile home.
"That fire went up so fast, I don't think I could have got there fast enough to do anything before the house burned down," he said.
Town residents are organizing a fundraising concert and auction for Wagner, as well as seeking donations online through Facebook, the Canadian Broadcasting Corp. said.