City employees are working to clean up debris after a water main break Monday caused a major flood in downtown Montreal.

During peak afternoon rush hour, water gushed onto the streets, covering a large area of the downtown core near McGill University. Mayor Michael Applebaum said the cause of the flooding appeared to be a break in a 120-centimetre (48-inch) water main, located in a construction zone on Pine Avenue near Peel Street.

The city said it's still

Water continues to flow near the McGill campus, although there is significantly less than the major flooding seen Monday.

University Street remains closed between Sherbrooke Street and Pine Avenue.

Classes are cancelled at McGill's Wilson Hall and Birks building. Classes at the Wong Building are being relocated.

The James Administration building is closed until noon Tuesday and the north entrance to the McConel Engineering Building is closed except for emergencies.

Officials are asking people to avoid the Milton Street entrance of the campus.

FACE School is also closed.

Montreal city crews worked overnight to clear the streets and re-salt streets and sidewalks. Montreal city crews worked overnight to clear the streets and re-salt streets and sidewalks. (CBC)

Workers fixed the water main break Monday evening, but crews worked overnight to clear the streets and re-salt streets and sidewalks.

As the water flooded onto the streets, Mayor Applebaum urged residents to be careful.

"We will continue to work without stop," Applebaum said Monday.

McGill expects 'extensive' damage

Officials are still trying to figure out what caused the break.

A note sent to employees at McGill warned of "severe flooding" on the campus and inside several buildings.

"We are trying to assess damage as best we can, but it will be extensive," the note stated.