The chief of a remote First Nation in northern Ontario says his community is devastated after a fatal fire on Wednesday that killed two children, aged six and one, and their 21-year-old aunt.

"The community and the leadership are distraught and shocked by the sudden tragedy that took these young lives," Rod Winnepetonga of Wunnumin Lake First Nation said in a statement Thursday afternoon.

Winnepetonga said smoke was coming out of a three-bedroom house around 9 a.m. on Wednesday when the local volunteer firefighter team responded, but the fire was already out of control.

Two investigators with Ontario's Fire Marshall's office were in Wunnumin Lake, about 500 km north of Thunder Bay, on Thursday to look into the cause of the fire.

The identity of the deceased is not being released until after a post mortem is conducted in Toronto.

A crisis team from a neighbouring First Nation is in Wunnumin Lake to offer support, but the chief said more help is needed to deal with the "heartbreaking loss."

"There is limited mental health professional support right now to address the grief, debriefing and individual counselling needed for the community and families," the news release stated.

The Grand Chief of the Nishnawbe Aski Nation said efforts to provide that kind of support are hampered by the cost of getting people into the fly-in community and by the shortage of accommodations.

"The first concern there is to stabilize, so we're not in crisis mode," Harvey Yesno said. "We've got to get the community back to functioning with the everyday way of life as quickly as possible."

Yesno said fatal fires are unfortunately common in remote First Nations where many homes are overcrowded and rely on wood stoves for heat.

About 600 people live in Wunnumin Lake.