Lake Waihola has again displayed high concentrations of potentially toxic cyanobacteria, sampling by the Otago Regional Council shows.
Visitors have been asked not to use the lake for recreational purposes and to obey cautionary signs, as the council issued a health warning for Lake Waihola yesterday.
Dog owners were also warned not to allow their pets to swim in the lake.
An earlier restriction for the lake was lifted two months ago.
Cyanobacteria, or blue-green algae, can produce toxins harmful to humans and animals if swallowed or contact is made with the skin.
Eating fish and shellfish from the lake should also be avoided.
Signs will remain in place until two consecutive samples indicate the volume of cyanobacteria has dropped to a safe level.
Anyone experiencing health symptoms after contact with contaminated water should visit their doctor.
