PROVO, Utah (AP) — Health officials are warning people not to swim on any part of Utah Lake as a toxic algal bloom spreads across the water for the third straight year.

The Utah County Health Department said in a statement Wednesday that several areas of the lake contain high levels of toxin-producing cyanobacteria.

They say people and pets should stay out of the water. Any fish caught at the lake should be cleaned well.

Commonly known as blue-green algae, cyanobacteria produce toxins that can cause headaches, fever, pains and nausea. It can be fatal for fish and dogs.

Cyanobacteria occur naturally in many freshwater systems and can proliferate rapidly under the right conditions of warm weather, plentiful sunshine and still, nutrient-rich water.

They can be fed by runoff from farms, lawns and industrial facilities.