A health warning has been issued for Canterbury's Lake Forsyth because of a potentially toxic blue-green algae found in the water.
The Canterbury District Heath Board says people and animals, especially dogs, should avoid the lake near Banks Peninsula until the warning is lifted.
Canterbury medical officer of health Dr Ramon Pink said the algae bloom could produce toxins harmful to humans and animals, and fish and shellfish from the lake should also be avoided.
Dr Pink said exposure to the water could cause skin rashes, nausea, stomach cramps, and tingling and numbness around the mouth and fingertips.
He said anyone who experienced these symptoms should visit their doctor immediately.