Griffith City Council has issued a red alert for Lake Wyangan North after the latest water samples revealed high levels of blue-green algae.
A red alert level warning indicates that people should not undertake recreational activities where they may be coming into direct contact with the water.
Warning signs have been placed at key recreational areas and will remain in place while high levels of blue-green algae are present.
People are advised not to enter the water, drink untreated water or bathe in water drawn from the lake while this warning is in place.
Before consumption, any fish caught should be cleaned and washed thoroughly in uncontaminated water and any internal organs disposed of appropriately.
Contact with the water may also pose a threat to livestock and pets.
Council will monitor the level of blue-green algae on a regular basis and provide updates via its website.