State authorities have issued a health alert for Pawnee Lake in Lancaster County and continued the warning for Rockford Lake in Gage County.

The Nebraska Department of Health and Human Services and other agencies on Friday cited an excess of toxins from blue-green algae in Pawnee Lake. Rockford's water tested out below the maximum level earlier this week, but the warning can't be lifted until that occurs two weeks in a row.

The algae, which scientists say are plantlike bacteria, are common in freshwater. Some types can produce dangerous toxins.

People can still camp, fish and boat on lakes under the alert but should not have full-body contact.

Drinking toxin-tainted water can cause vomiting, diarrhea, respiratory failure and, rarely, death.