(CNN) -- Trapped residents screamed for help from their balconies as flames tore through a senior retirement complex in Quebec last week.
Since then, the sound of machines has filled the air as investigators try to thaw the ice-encrusted rubble to search for victims and evidence of what caused the deadly blaze.
At least 10 people were killed in the fire, which struck the 52-unit Residence du Havre in L'Isle-Verte, Quebec, early Thursday morning. Police believe 22 others also perished, but they're still searching the scene to find out for sure.
"This is something we could have never imagined," Nicole Belanger, who worked in the residence, told Canadian broadcaster CTV. "The heart of our village is now gone."
Mourners in the tiny town of about 1,500 people gathered for a Mass to honor the victims Sunday. Some carried photos of their loved ones.
One woman told CTV her in-laws had died in the fire.
"They just moved in two months ago," she said. "We wanted them to be in a safe place for the winter."
At least 37 of the residents were older than 85, according to government documents obtained by CBC.
Many of them had Alzheimer's disease and used wheelchairs or walkers, acting Mayor Ginette Caron told CBC.
Nelida Pettigrew, 90, told CBC she left her walker behind, escaping down two flights of stairs to safety after a neighbor pointer her toward the emergency exit. But others didn't make it.
"I saw them. It was horrible, but I'm OK," she said. "I didn't cry then, but I cried after."
Investigators are still trying to determine what caused the blaze.
A lit cigarette is one of many possibilities authorities are looking into, but police say they have not ruled anything out as they try and determine a cause.
Quebec Premier Pauline Marois told reporters Sunday that the situation was an "unacceptable" tragedy, according to CBC, but cautioned that people should avoid speculation about what caused the fire and allow the investigation to run its course.
Frigid temperatures have made searching the scene a struggle.
Authorities are now using machines normally used to de-ice ships in their efforts to thaw the rubble.
CNN's Paula Newton contributed to this report.