The cause of the fire in Wunnumin Lake First Nation is under investigation.
All three of the dead are female — a 21-year-old, a six-year-old and a one-year-old. Their names are not being released until their immediate family has been notified.
A news release from the First Nation says the community "has been devastated by this tragedy."
Crisis teams from surrounding First Nations are on their way to Wunnumin Lake to support those who are grieving.
About 600 people live in Wunnumin Lake, located 500 km north of Thunder Bay.