Officials said in a news release that the alerts were issued following water tests.
Alerts continue at Rockford Lake in Gage County and Maple Creek Recreation Area Lake in Colfax County. An alert for Holmes Lake in Lincoln has ended.
Skin exposed to the toxin can develop rashes and blisters, and drinking tainted water could cause headaches, nausea and muscle pain.
When a health alert is issued, signs are posted advising 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 water exposure.