State health and environment officials have issued a health alert for toxic blue-green algae at Kirkman's Cove near Humboldt in the southeastern corner of Nebraska. An alert has also been issued for Maple Creek Recreation Area Lake in Colfax County. Officials said in a news release Friday that the alerts were issued following tests of the lakes' water. Skin exposed to the toxin from the algae can develop rashes and blisters. Someone who drinks water containing the toxin is at risk for headaches, nausea and muscular pain. When a health alert is issued, signs are posted to advise the public to use caution, and designated swimming beaches are closed. Recreational boating and fishing are permitted, but the public is warned to use caution and avoid exposure to the water.