Eight others were injured in the overnight fire, which tore through a 36-unit apartment building on Des Merisiers Avenue, about 100 kilometres northeast of Montreal. The building is a total loss, leaving all of its residents homeless.
The building did not have doors in the door frames next to the stairs, allowing the fire and smoke to spread quickly.
Residents said the building was equipped with fire alarms, but it is not yet known whether there were sprinklers.
Burned 'like a house of cards'
Isabelle Sawyer, a resident of the building, said she managed to get out after her neighbour banged on her door and warned her about the fire.
"It burned like a house of cards," Sawyer said.
"I heard people screaming on the balconies. It was apocalyptic."
Sawyer said many of the units in the building are one-bedroom, occupied by single people, many with no insurance and on social assistance.
Investigators are studying a number of hypotheses, including the possibility that the flames originated with a cooking fire.
The City of Drummondville is taking donations for the victims, while Ressourcerie Transition and Vestiaire La Penderie are taking donations of furniture and clothing, respectively.
The Red Cross, which has provided temporary housing and food to the victims, is also accepting donations to its general fund.