Toxic algae is continuing to stop people from entering the water at one of Llanelli’s most popular sunny-day destinations.
Natural Resources Wales confirmed the presence of the algae at North Dock after analysis of water samples from the dock.
Tests will continue to be carried out on the site until two negative tests for the algae are recorded.
The Llanelli sprint triathlon is set to take place at the Dock on May 13, with organisers being kept updated on the algae situation.
Authorities said the blue-green algae could be harmful to both humans and animals, and have advised the public not to enter or swallow the water.
Pets and livestock should also be kept away from the water, with notices regarding safety in position around the lake.
According to Public Health Wales, blue-green algae cannot be seen with the naked eye unless concentrated into clumps, when it can appear as green flakes, greenish bundles or brown dots in the water.
The algae is a type of bacteria which can be found naturally in many inland waters, estuaries and the sea. It can affect the quality of the water and produce toxins which can kill wild animals and other aquatic life, and be harmful to human health.
The toxins can cause skin rashes, nausea, vomiting, stomach pains, fever and headaches.
They can infrequently cause more serious illness such as liver and brain damage. Children are at greater risk than adults of developing problems because of their lower body weight.
An annual feature of water bodies across Wales, there are no quick and easy remedies for its control according to Public Health Wales.
County executive board member for environment and public health, Councillor Philip Hughes, said: “The build-up of blue green algae is a natural occurrence which happens from time to time.
“We would urge people to abide by the warning we have issued as public safety is our main priority. We will continue to monitor the situation and keep members of the public updated.”
A spokesman for Natural Resource Wales said: "Currently Carmarthen County Council and NRW are working to find a solution to the blue green algal issue that has been identified at North Dock, Llanelli.
"The initial sample found that the algae were at numbers above the warning threshold for blue green algal blooms.
"Until there are two samples with algal numbers below the warning threshold then a precautionary approach should be taken as all blue green algae have the potential to produce cytotoxins."
If you have any health concerns, please contact your GP or NHS Direct Wales on 111.
To report any further signs of blue green algae call Natural Resources Wales 24 hour hotline on 0300 065 3000.
