About 40,000 residents in the old city of Gatineau are being asked to boil water for at least a minute before consuming it or brushing their teeth with it.
The boil water advisory began Thursday night and city officials said Friday that it may last for two to three days.
It's the result of an electrical generator problem that interrupted the system regulating chlorine levels in the water.
The Gatineau hospital on la Vérendrye Boulevard is affected but remains open. Water bottles are being distributed.
Schools in the area also remain open after water was delivered Friday morning. Water fountains have been covered up and signs warning students have been placed in washrooms, said officials with Commission scolaire des Draveurs.