Canada's prime minister Stephen Harper warned there was little doubt the death toll would be high. Officials said firefighters saw and heard people in the building that they were unable to save.
Many of those unaccounted for were confined to wheelchairs and only five residents in the centre were fully able to care for themselves, said Ginette Caron, acting mayor of the small town of L'Isle-Verte, about 140 miles from Quebec City.
Firefighters arrived within eight minutes of getting the alarm and several fire departments in the region were called in to help.
But they were unable to carry out a complete evacuation because of the intensity of the blaze. About 20 residents were transported to safety.
Pascal Fillion, who lives near the home, said rescuers felt helpless against a fast-moving blaze with thick smoke.