The Mounties were initially called in to set fire to 7th Street SE around 1 a.m. Sunday.
When police arrived at the scene, firefighters were working to put out the blaze.
As soon as the fire was extinguished, three people were found dead inside the house.  The RCMP noted that these deaths are considered suspicious.
Police have detained a man.
The RCMP’s main crime services, the Forensics Department, the Portage la Prairie and the Office of the Fire Chief are conducting investigations.