Tipperary County Council has issued a warning over algae bloom on certain parts of Lough Derg following the recent spate of warm weather.
The blue green algae, which contains toxins, has been reported around Youghal near Newtown, Nenagh.
The bloom, which forms a green scum and is generally close to the shore, can cause skin irritation in humans if touched and can kill animals.
It is known to have caused the deaths of at least three dogs over the past few years and pet owners are being warned to be careful of allowing their dogs to drink from the lake. The council is advising that if you have a pet to bring an alternative source of drinking water if you are visiting the lake.
Tipperary County Council may be contacted at 0761-065000.