Provincial police say the Sioux Lookout detachment and the Lac Seul Police Service responded to a call early Saturday afternoon reporting an unresponsive person at a residence.
Investigators say they found three people unresponsive when they arrived, who were pronounced dead at the scene.
They say autopsies will be done later this week in Toronto to determine the cause of death.
Police have not identified the deceased, but do not believe there is a risk to public safety.
They are asking anyone with information to get in touch.