Officers say the Bel-Air Manor building was deliberately set ablaze in the early morning hours of Oct. 31, 1993.
Mounties say most residents were able to escape, but two women from different suites were trapped in a smoke-filled hallway and died.
Sixty-five-year-old Agda Easingwood was found by firefighters but died later of her injuries.
After the fire was extinguished, 20-year-old Valerie Diner's body was found in the ruin.
Investigators say all leads in the homicides have dried up, and police are again asking anyone who might have seen what happened to come forward.