Vulnerable members of the Chipewyan Prairie First Nation have been relocated after the water treatment plant that supplies the region was shut down.
Alberta Health Services issued an advisory on Friday after a mistake at the plant in Janvier. It could take more than a week to turn the taps back on.
"Water quality may have been impacted when the chemical used in the filtration process (polyaluminum chloride) was mixed with the chemical used in the disinfectant process (sodium hypochlorite)," the Regional Municipality of Wood Buffalo said on its website.
"These are the regular chemicals used while treating water, but they should not be combined at the same stage in the treatment process."
The public was not exposed to the contaminated water, the municipality said.
Janvier itself has not been evacuated, but officials did provide seven buses for the relocation of the First Nations members. About 50 people were moved to Fort McMurray on Monday evening.
It said people who decide to stay in Janvier, about 120 kilometres south of Fort McMurray, Alta., will be supplied bottled water. Buildings that receive trucked water for their cisterns are not affected.
It will take between seven to 10 days to clean the water plant, That will include removing the chemicals, cleaning the reservoir and reinstalling the tank, the municipality said.
"There is an ongoing investigation into the cause of the incident," it said. "Once determined, we will be reviewing the current system and procedures and putting additional controls in place to help ensure we avoid future disruptions to the supply of water."
Janvier's elementary school, Father R. Perin School, has been closed. The Northland School Division said it would have been too difficult to maintain health standards if the building had remained open.
Janvier is about 400 kilometres northeast of Edmonton.
With files from The Canadian Press
