An initial ban advised all residents living around the Mount Polley mine area, near the town of Likely, to use only bottled water until further notice.
The advisory affected hundreds of people living around Quesnel Lake, Polley Lake, Hazeltine Creek and Cariboo Creek.
The ban has since been expanded to include anyone living along the Quesnel and Cariboo Rivers.
Authorities are asking people in the region to stop using water from both rivers.
Those areas are sparsely populated and the Cariboo Regional District has not determined how many people have been affected.
People in Quesnel are also being asked to avoid using water from the Quesnel River.
The ban does not apply to people in Williams Lake or other towns along the Fraser River.
Authorities had previously said Likely was not directly affected, because it was unclear how many people in the town used water from Quesnel Lake.
But since then, the Cariboo Regional District has decided to start delivering water to Likely because the main supplier of bottled water in the area, a small grocery store, could not keep up with the demand.
Al Richmond, chair of the district, said search and rescue crews evacuated campers in the Mount Polley area. But shelters have not been provided for them, as they appear to have set up camp elsewhere without any problems.
Early Monday morning, the earthen dam holding waste water from the Mount Polley mine was breached, sending its contents into Hazeltine Creek, Richmond said.
He said most of the waste appears to have been contained in the creek, though some of the material has flowed into Quesnel Lake and Polley Lake.
"The majority of the slurry and the debris was contained at the mouth of the creek," said Richmond. "While there has been some flow of that material into the lake, it hasn't been substantial in consideration of the size of the spill."
The width of the creek has swollen in size because of the washout.
"At one time it was four feet and now it's 150 feet," he said.
The Horsefly-Likely Road, which joins Likely to the town of Horsefly, has been washed out, and authorities have closed it down until cleanup crews finish making repairs.
The Cariboo Regional District has not received any reports of injuries or people getting sick from drinking water.
No property damage reports have been filed, though that may change with time, Richmond said.
The Ministry of Environment said it is working to determine how much environmental damage has been done.
"Further monitoring and testing of waterways will be required before the full extent of potential environmental impacts can be determined," the ministry said in a written statement.
Water test results are expected in days.
No other details have been released as authorities are trying to determine the cause and extent of the breach.
Mount Polley is an open pit copper and gold mine owned by the Imperial Metals Corporation (TSX:III).
The company has been involved on the construction or operation of seven mines, the majority in British Columbia.
Requests for comment from Imperial were not immediately returned.
Tailings ponds contain waste water from mines.
-By Steven Chua in Vancouver.
Note to readers: A previous version wrongly stated the name of the road joining Horsefly and Likely. The correct name is in fact the Horsefly-Likely Road.
A previous version wrongly stated the mine is in the town of Likely. In fact, it is outside the town.
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