Some media have reported that a smoker at the residence in L'Isle-Verte caused the fire, which killed 10 people and has left another 22 presumed dead.
"What's been said is one hypothesis among many," Quebec provincial police Lt. Guy Lapointe told a news conference.
"When you conduct an investigation of this magnitude, you have to determine all the facts and not simply just one or two in order to achieve a conclusion.
"For us, there are still many hypotheses on the table."
At a later news conference, Lt. Michel Brunet was cautious about attributing the cause to anything in particular.
"It could be a cigarette, it could be a small heater, it could be an electrical problem," Brunet said. "We have to be sure at 100 per cent."
"We're going to take the time we need."
The official death toll increased to 10 on Saturday, with the number of those missing revised downward to 22.
But Lapointe wasn't holding out much hope for those whose remains have not yet been found.
"I think we can all agree here today that the...people who are still missing, I think we can assume the worst," he said. "But we're not going to confirm any deaths until we've actually recovered the remains."
Frigid temperatures continued to hamper the search, with Lapointe saying the ice in certain places was as thick as 60 centimetres.
"So you can imagine how difficult it is to go through the ice, melt it, and do it in a way that we preserve the integrity of potential victims," he said. "So it's very difficult work again today. It's very cold."
To speed up proceedings, equipment that pushes out very hot air and is normally used to de-ice ships was brought in.
The search will resume on Sunday.
The coroner's office identified two victims on Saturday: Juliette Saindon, 95, and Marie-Laureat Dube, 82. A third person has been identified but his or her name will be released only on Sunday.
Genevieve Guilbault explained the procedure for officially releasing the names of the deceased.
"When a victim is formally identified by the coroner, we always inform the family first," she said.
"Then we wait, out of respect and courtesy for them, 24 hours before we give the information to the public and to the media."
A mass is scheduled at the church in L'Isle-Verte on Sunday afternoon.
Priest Gilles Frigon described it as an event where residents can gather and share their grief. He has invited loved ones to bring photos of the deceased and the missing.
The mass will be a simple one, with Frigon saying he wants to give first responders the opportunity to express their suffering.
"It will be family-oriented and intimate, so that in this tragic event we're going through, we can find ourselves and rebuild our hearts," Frigon said.
"It will be about the grief of people who are affected by the loss of their father, their mother, their grandfather, their grandmother, their great-grandfather and their great-grandmother."
Quebec Premier Pauline Marois has said she will visit L'Isle-Verte on Sunday, but it is unclear whether she will attend the mass.
A more official commemorative ceremony featuring dignitaries has been set for Saturday, Feb. 1.
Meanwhile, the Red Cross announced Saturday it has raised $200,000 for the community. The money will go to various things like eyeglasses, furniture and clothing.
— With files in Montreal from Donald McKenzie
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