The latest sample by Thurston County environmental health officials found 39.2 parts per million of the toxic algae Microsystin. The recreational advisory limit set by the state is 6 ppm.
The lake will remain posted with a warning sign and be monitored weekly until the algae bloom dies off or until it stops producing toxins, health officials said.
Toxic blue green algae is also present in Lake St. Clair and Black Lake, but at levels well below the health advisory threshold.
However, health officials urge caution in lakes showing the presence of the toxic algae because it can be more concentrated in areas where the algae scum is thick. Lake St. Clair and Black Lake will continue to be monitored weekly.