Lake Tapps closed to swimmers after the health department received more than a dozen illness reports from people who swam in the waters last weekend.
Tacoma-Pierce County Health Department found toxic algae present at the lake, but officials say it is too early to tell if people became sick from toxic algae.
“We are investigating the potential link between the toxic algae bloom and the symptoms people have reported, but there is no definitive laboratory test for toxic algae illness,” Brad Harp, water resources program manager.
The Health Department has not found toxic algae in Lake Tapps previously.
Water with algae contamination could cause gastrointestinal problems if ingested.
People who were sick reported symptoms that are consistent with ingestion of microcystin, a toxin produced by several genera of cyanobacteria, including Oscillatoria. The illnesses occurred in people ages 2 to 48 years; they all recovered within 48 hours.
The Health Department is urging people to stay out of the lake. .
People should not swim, wade or fish at Lake Tapps, and they should keep their pets from going in the water.