SALT LAKE CITY (AP) — The Utah Department of Environmental Quality is advising beachgoers that three more Utah reservoirs have outbreaks of harmful algal blooms.

The Deseret News reports that warnings went up at Rockport, Echo and Deer Creek reservoirs on Tuesday, joining six other Utah water bodies that are suffering from the blue-green algae.

The algal blooms can contain toxins that can cause serious illness in people and animals. They are a byproduct of excess nutrients of phosphorus and nitrogen in the water. One source of those nutrients is wastewater discharge.

Nutrient pollution can also be caused by urban runoff and agricultural activities.

Utah Lake has suffered from outbreaks over the past several years, including a 2016 infestation that covered most its surface.

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Information from: Deseret News, http://www.deseretnews.com