Health authorities have warned about the toxic algal bloom reappearance in Lake Waihola and Tomahawk Lagoon.

John Threlfall, Otago Regional Council director of environmental information and science, has affirmed that a sample was taken from the lake and the algal blooms presence was then confirmed.

Now, when the toxic blue-green algae presence has been confirmed, health authorities have passed a word of caution in which they have asked people to avoid the area, where algae is present. They should take caution when carrying out activities like fishing and boating.

There are some people, who can develop allergic reaction from the algae bloom. For them, it is very important to exercise caution.

''At the moment, the water in Lake Waihola looks very green. This is due to this algae species which belongs to the `cyanobacteria' group of algae", affirmed Threlfall.

He continued by affirming that this group of algae is such that it secretes harmful toxins, which when released in the water can make people and animals ill. The council has affirmed that it was only after tests that toxicity of the algal blooms got revealed as otherwise they were following the guidelines made by the Ministry for the Environment.