LINCOLN, Neb. (AP) — State health and environment officials have ended a health alert for toxic blue-green algae at Branched Oak Lake in Lancaster County.

The alerts will continue for at least another week at Iron Horse Trail Lake in Pawnee County, Pawnee Lake in Lancaster County and Willow Creek Lake in Pierce County.

Officials said in a news release Friday that the alerts were issued following tests of the lake water. Lakes that are on health alerts must have two consecutive weeks of readings below the threshold before the alerts are discontinued.

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.