L'ISLE-VERTE, Quebec – The small grief-struck Quebec town of L'Isle-Verte will hold a memorial service on Sunday for the 32 people who died in a massive fire that engulfed a three-storey wooden residence for seniors.

Despite media reports alleging a cigarette ignited the blaze early on Thursday, police say they still do not know the cause of what appears be Canada's second-most deadly disaster in a retirement home.

Ten bodies have been recovered and 22 people are still missing in the frozen ruins of the Residence du Havre in L'Isle-Verte, a town of 1,500 people on the St. Lawrence River northeast of Quebec City and 65 km (40 miles) north of Maine.

The memorial service, due to start at 2 p.m. EST (1900 GMT), will be led by local priest Gilles Frigon. He said the church wanted to help rebuild the hearts of the community.

"We celebrate with them but when they suffer, we suffer," he told reporters tearfully on Saturday. A larger public mass is due to be held in the town on Feb. 1.

Special teams of police, firefighters and coroner's office officials, braving brutal cold, have been using steam and hot air to melt thick ice encasing the bodies of victims in the burned ruins of the residence.

Police said the teams would focus on melting the ice overnight before splitting into two groups on Sunday, with one set of specialists continuing to attack the ice while the other would look for the remains of victims.

"We are working stubbornly and rigorously to establish the cause and circumstances of this fire while preserving the integrity of the potential victims," Quebec police spokesman Michel Brunet told reporters as night fell on Saturday.

The disaster looks set to be the second worst to hit a Canadian seniors' home after a 1969 blaze in Quebec that killed 54 people.

Only part of the residence was equipped with sprinklers. Quebec law does not require sprinkler systems in residences where the occupants have some mobility.

Quebec Premier Pauline Marois cut short a visit to Europe and plans to be present at the service to mark the province's second calamity in a matter of months.

In July 2013, a runaway tanker train carrying light crude from North Dakota's Bakken region derailed and exploded in the heart of the town of Lac Megantic, Quebec, killing 47.

Brunet said that while he appreciated locals were impatient to know what had happened, it could take months to determine the cause of the fire.

The teams on the ground are using special equipment to melt the ice, which in some places is up to 2 feet (60 cm) deep - testament to how much water firefighters had to use in the early hours of Thursday, when temperatures hovered around minus 22 Celsius (minus 8 Fahrenheit).

The specialists are working inside canvas tents to help concentrate the heat on the ice.

"Sixty centimeters of ice obviously takes a long time to melt naturally and in the temperatures we have now, that's not going to happen at all. So the equipment and covers we have will enable us to progress a lot more rapidly," said Brunet.