Residents said a one-year-old girl, a six-year-old girl and their aunt, a 21-year-old woman, were killed in the blaze that ravaged a home in the Wunnumin Lake First Nation. Their names were not immediately released.
"It's pretty hard for us right now," said Rod Winnipetonga, chief of the First Nation, which is located about 500 kilometres north of Thunder Bay.
"Right now, I'm looking for any assistance that any communities can provide."
The fire broke out Wednesday at about 9 a.m. in a house shared by multiple members of one family, said community leader Sol Mamakwa, adding that the mother of the children who died in the blaze wasn't home at the time.
Many residents, who were starting their day when the fire broke, stood helplessly by as flames destroyed the residence, Mamakwa said.
"There were lots of bystanders, lots of community members that were very distraught," he said. "The leadership and the community are very distraught and shocked over the loss."
One man, a member of the community council, made several failed attempts to get into the home and rescue the three who died.
"He was one of the ones just on his way to work," said Mamakwa. "He actually got discharged out of hospital just this morning, so he's OK."
Relatives of the victims are currently being housed with other family members as the community works to support them.
The entire tight-knit reserve of about 600 people, however, was still in shock Thursday.
Crisis teams were working to help residents deal with the tragedy, but Mamakwa said more professional support was needed.
"It seems there is limited mental-health professional support to deal with the grief, to deal with the grieving, individual counselling, all of that. That's kind of where the support is lacking there," he said.
A spokeswoman for the federal aboriginal affairs department says officials have reached out to the community to ensure it has the support it needs.
Sgt. Jackie George of the Nishnawbe-Aski Police Service said a post-mortem examination for the victims was to take place in Toronto, however no date has been set.
The cause of the fire wasn't immediately known.
Officials with the Ontario Fire Marshal's office were in the community Thursday to investigate the blaze. They were called in at the request of the Wunnumin Lake council and Ontario Provincial Police.
The community is accessed primarily through air transportation, although it can also be reached during certain seasons by winter roads or waterways.
— By Diana Mehta in Toronto.