The U.S. Forest Service says a sewer line is leaking near Camp Richardson Resort on the south shore.
Tests found high levels of the bacteria in the water from Jameson Beach to the Valhalla Boathouse.
No illnesses have been reported, but people are advised to stay out of the water until it clears up.
Tests in other parts of the lake came up clean.
Crews are repairing the leaking sewer line.
For more information, click here.
If you're on the ABC7 News app, click here to watch live