A small number of water samples taken near the site of a major spill at Imperial Metals Corp's Mount Polley mine have shown copper levels high enough to pose a risk to fish, British Columbia officials said on Friday, but the copper did not exceed drinking water guidelines.

The local public health authority believes drinking water intake pipes have not been exposed to unsafe levels of contamination, Medical Health Officer Sue Pollock said on a conference call with reporters.

The copper and gold mine's tailings dam burst on Aug. 4, spilling billions of gallons of sludge down waterways, including a lake that is a popular fishing spot and important salmon habitat.

Two samples taken deep in Quesnel Lake on Aug. 12 showed high concentrations of copper, 134 micrograms per liter and 217 micrograms per liter, according to documents posted by the province on Friday. To meet water quality guidelines for even short-term or "acute" exposure for fish, copper levels should be 8.5 micrograms per liter or less.

Four other samples narrowly exceeded chronic or acute guidelines for copper exposure by aquatic life. Further samples taken in other areas were within guidelines.

Last week, British Columbia's Ministry of the Environment said sediment collected from Quesnel Lake had exceeded some standards, but that metals were not likely to seep out of the sediment and harm water quality in the future. More testing is underway.