LINCOLN, Neb. (AP) — State health and environment officials have issued a health alert for toxic blue-green algae at Willow Creek Reservoir in Pierce County. An alert is continuing for Rockford Lake near Beatrice in southeastern Nebraska.

The alerts were issued following tests of the lakes’ water. Signs have been posted at the lakes, urging people not to swim in them. People can still use the lakes’ public areas for other activities.

Skin exposed to the toxin from certain strains of blue-green algae can develop rashes and blisters. Someone who drinks water containing the toxin is at risk for headaches, nausea and muscular pain.