The Lester B. Pearson School Board shut all its buildings Thursday after engineers recommended the closures as a "precautionary measure" given concerns about heavy rooftop snow.

All schools, training centres and administrative offices are closed until further notice, giving students and staff an extra day off before Easter weekend.

The closures affect 41 elementary schools, 12 high schools, two adult education centres and four vocational training centres between Verdun and St. Lazare in the western region of Montreal Island.

The closures were announced Wednesday night after school board engineers reported an increased risk of roof collapses caused by the weight of snow accumulation.

The roofs were stable last week but engineers are concerned about a layer of ice that has since formed, said board chairman Marcus Tabachnick. 

"This is just part of the monitoring process," he told CBC News. "What happened yesterday was the change in the weather, and the amount of rain that fell has changed the density and the amount of snow that is currently on the roofs."

Maintenance crews have been removing snow since March 12 and will continue clearing roofs over Easter weekend, the board said.

Meanwhile, most students at the Montreal French school board (CSDM) returned to class Thursday after several days off. School had been cancelled to allow rooftop snow clearing.

Five CSDM schools and centres will remain closed over the long weekend, reopening March 25, the board said.

The French board will make up lost classes on one of two scheduled professional days later this spring.

Record-breaking snowfalls in some regions of Quebec this winter have caused several building cave-ins that have killed four people in the last week.