An investigation into the cause of blue-green algae at Llyn Clywedog near Llanidloes has come back as "inconclusive".

The reservoir was closed off to the public earlier this year after Powys Council recommended that people should not swim, allow pets or livestock to come into contact with the water or eat fish caught in the reservoir.

The algae produces toxins which can cause skin rashes, nausea, vomiting, stomach pains, fever and headaches.

Natural Resources Wales has since said that their investigation has not revealed the cause of the algae.

David Lee, NRW Environment Team Leader for North Powys said: "Our officers have investigated a number of potential causes of the blue-green algae at Llyn Clywedog. The result of the investigation has been inconclusive. We continue to monitor the lake for any significant changes."

Anyone who has concerns on incidents of blue-green algal blooms or scums is urged to call the Natural Resources Wales 24-hour incident hotline on 0300 065 3000 or report it online at naturalresources.wales

Algae occurs naturally in inland water, estuaries and the sea and is an important part of the water life cycle but can grow into large blooms rapidly during warm weather and can produce toxins. This excessive growth can be particularly common at this time of year and is known as a ‘bloom’.

Further information on Blue-Green algae can be found on the Natural Resources Wales/Blue-green algae website.