A health warning issued for Otautu Bay last month has now been extended to include all of Lake Rotoehu.
The public is also advised that Lake Okaro, near Rotorua, is unsafe with an algal bloom.
Routine monitoring conducted by the Bay of Plenty Regional Council confirmed blooms of potentially toxic blue-green algae at both locations.
Medical Officer of Health Dr Phil Shoemack said the health warnings meant people should avoid any activity which results in significant contact with the lake water.
Contact with water affected by blooms of blue-green algae could cause asthma and hayfever attacks, skin rashes, stomach upsets, and in some cases neurological effects such as tingling around the mouth, headaches, breathing difficulties and visual problems.
