OTTAWA  - Canadian police and firefighters used steam machines on Friday to melt thick ice encasing the corpses of elderly people who died in a massive blaze that destroyed a wooden retirement residence in rural Quebec the day before.

Police said that five people died and about 30 were unaccounted for after the early morning blaze ripped through the Residence du Havre in the small community of L'Isle-Verte, about 230 km (140 miles) northeast of Quebec City.

A firefighter sprays water at the Residence du Havre after a fire in L'Isle Verte, Quebec, January 23, 2014. [Photo/Agencies]

Police said the missing might not all be dead since it was still unclear how many of the home's residents were in the building when the fire started.

The disaster has already raised demands that the Quebec government require homes for the elderly to be equipped with sprinkler systems, following the lead of neighboring Ontario. Only part of the Isle-Verte residence had sprinklers.

"If the investigation shows that we need sprinklers or new rules, the government will act and bring in the changes for sure," said Jean-Thomas Grantham, spokesman for Quebec Labor and Social Solidarity Minister Agnes Maltais.

The ice formed as firefighters, working in temperatures that dropped as low as minus 22 Celsius (minus 8 Fahrenheit), doused the building with water for hours. In some cases the resulting ice is one or two feet (30 to 60 cm) thick.

"So many things could happen that we can't plan on - the cold is extreme, the equipment could freeze, we could run into other issues," said Guy Lapointe, spokesman for the Quebec provincial police force.

"The steam is being used for us to be able to advance at the scene, being able to preserve the integrity of potential victims."

The cold was so intense on Friday that teams of police, firefighters and coroner's office officials could only work in 45-minute shifts.

Police have not managed to track down all the residents who might have been in the building at the time of the fire, and Lapointe said it is possible that nonresidents had been in the building.

Officials said they do not know what caused the fire and Lapointe appealed to local residents to provide any videos or pictures they may have taken after the fire started shortly after Wednesday midnight.