A precautionary boil water advisory was issued for much of the west side of Saskatoon, following a major water main break Friday morning.

In an update, later in the day, the city said the advisory was still in place for the following areas:

River Heights.

Kelsey Woodlawn.

Lawson Heights.

Silverwood.

Hudson Bay Industrial.

Marquis Industrial.

North Industrial.

Agriplace.

Residents in those neighbourhoods were being asked to boil their drinking water.

The city said those areas saw a significant drop in water pressure and the advisory was necessary for health safety.

It said water samples are being tested and results should be known by Monday when the boil water advisory will be reassessed.

Other parts of Saskatoon which had lost water service, temporarily, were deemed to be safe and no boiling was necessary .

The city said they believe a water main broke around 2 a.m. CST Friday, roughly south of 45th Street East and 1st Avenue North.

Residents noticed problems with water service first thing Friday morning, with some reporting no water coming from taps in the downtown and reduced low water pressure elsewhere.

Near the corner of 46th Street and Faithfull Avenue, a virtual lake had been created with knee-deep water in some points, according to CBC News reporter Dan Zakreksi.

Water pressure was also reported to be low in the Dundonald area in the city's northwest.

For a while, it looked like students at one high school would have the day off. Classes were cancelled at Bishop James Mahoney High School, but then the water pressure came back and the school decided it would stay open.

Water was restored throughout the city later in the morning.