The blue-green algae bloom reported at Olympia's Summit Lake on Tuesday is toxic, according to the Thurston County Health Department.
The department released laboratory test results Friday morning showing the algae bloom is producing high levels of the neurotoxin Anatoxin-A.
Toxin levels found in the sample were at 9.95 micrograms/liter. A sample that returns results of 1 microgram/liter or higher is considered a health concern, the department says.
More information about blue-green algae blooms, and its health concerns, is available on the county's website.
Water that contains toxic blue-green algae can cause illness, including stomach pain, vomiting and diarrhea, as well as allergic reactions, the website says.
For pets, exposure to the toxins can result in loss of appetite, salivation, vomiting, weakness, seizures, convulsions and difficulty breathing.
The health department advises Summit Lake residents and visitors to take extra precautions while the algae bloom is present. People, pets and livestock should avoid contact with the water where the algae blooms are present. Fish caught should be released.
And people and pets should not drink the water.
The next sample will be collected for testing Monday.