The city of Maple Valley has closed the Lake Wilderness beach area because of a toxic blue-green algae identified as Anabaena flos-aquae.

A city press release stated the algae may threaten the health of people and pets if ingested.

The city posted warning signs at Lake Wilderness and closed the beach Friday. Young children and dogs are particularly at risk.

The blue-green algae collect at the shoreline

where young children may get it in their mouths and dogs may drink from the water. Common symptoms include nausea, vomiting, diarrhea and eye or skin irritation.

A sample taken from a band of scum along the beach last week measured well above the state recreational standard and as a precaution, the city has issued the warning to lake users.

The species of algae have been known to thrive in lakes until winter cold and rains decrease the population.

The lake will be tested weekly until the threat is determined to be over.

Warning signs will be posted at primary access areas, notifying lake users of the danger. They will be left in place as long as the threat continues. City officials ask lake users to be vigilant with your children and pets when near the water.

If any water with a visible green scum is ingested, notify your doctor or veterinary and follow their suggestion. Visit the city Web site. For further information please contact Sally Abella, science and technical support, King County Water and Land Resources Division at 206-296-8382 or by e-mail at sally.abella@kingcounty.gov.