LINCOLN, Neb. (AP) — State officials say a health alert remains in effect for a fourth straight week at Bluestem Lake in Lancaster County.

The latest alert notice comes after testing this week detected toxin levels produced by blue-green algal blooms.

Officials say visitors to the lake should avoid full body contact activities such as swimming, wading, skiing and jet skiing. Non-contact activities such as boating, fishing and camping should be safe. People also are urged to keep pets out of the water and not allow them to drink lake water.

Skin exposed to the toxin can develop rashes and blisters. Ingesting the toxin can cause headaches, nausea and muscular pain.