Two people discovered unconscious in a Salaberry-de-Valleyfield residence on Friday have died.
The 45-year-old man and 39-year-old woman were found inanimate in a house on Ellice St.
Both were in critical condition when emergency personnel found them.
The Surete du Quebec’s Major Crimes unit opened an investigation into the deaths.
Investigators believed the deaths were due to carbon monoxide poisoning but could not say whether it was accidental or voluntary.