Water sports have been banned at a popular lake with tourists in the Brecon Beacons National Park, Wales, after blue-green algae was identified.
Llangors Lake, in Powys, is popular with water skiers, sailors and anglers, but the Powys council's environmental health service made the decision following information from Public Health Wales and the Environment Agency.
Pet owners and parent have also been warned to keep their animals and children away from the water, as blue-green algae contains toxins that can cause skin rashes, eye irritation, vomiting, diarrhoea, and muscle pain.
Children are at a greater risk of suffering effects because of their lower body weight.
The council's public protection manager, Steve Clinton, told the BBC: "Blue-green algae has the potential to cause illness if swallowed or even by just coming into contact with it.
"Blue-green algae occurs naturally in inland waters, estuaries and seas and cannot be removed or treated."
Park conservation manager Paul Sinnadurai also told the site: "Llangors Lake is a popular destination for locals and visitors and is an important site for water recreation, walking and bird watching.
"It's really important that people pay attention to these warning notices and make sure their children and their pets avoid contact with affected water."
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