HAYDEN LAKE - A health advisory was issued Thursday for Hayden Lake by the Panhandle Health District and the Idaho Department of Environmental Quality.

Water samples confirmed the presence of the blue-green algae Anabaena circinalis in the northern end of the lake.

"This algae species may produce potentially dangerous toxins." according to a press release.

In animals, a toxin that may be produced by Anabaena circinaliscan can cause a rapid progression of neurological symptoms such as muscle spasm, decreased movement, labored breathing, convulsions and death.

Symptoms have not been documented in people. However, the public is advised to avoid any activity that could lead to ingesting the lake water considering the effect Anabaena circinalis has on animals, the release said.

Bob Steed with the Department of Environmental Quality said the blue-green algae was recently discovered by a Hayden Lake resident who reported finding scum in the water near a dock on the north end of the lake.

Additional samples and lab tests confirmed it was blue-green algae, which was last confirmed in Hayden Lake in 2007.

Steed said a combination of temperature and nutrients in the water produces the algae, which was also found in Fernan Lake earlier this summer.

Blue-green algae are naturally occurring, microscopic bacteria.

There is no action plan, other than time, to eliminate the algae. The DEQ hopes to see Hayden Lake clear of the algae within two weeks.

People are warned to be wary "where water is an uncharacteristic green color and where unsightly thick green mats are present along shorelines. Drinking water from the lake may be dangerous if toxins are present; the toxins cannot be removed by boiling or filtering the water." Children and pets are particularly susceptible.

The blue-green algae was found on the north end of the lake. Swimming is still OK at Honeysuckle Beach.

DEQ said the public will be advised when the concern no longer exists.