At least 10,000 fish have died following a "major" pollution incident in a Powys river.

Natural Resources Wales says it is following a "number of leads" and an investigation is ongoing to find the source of the incident that was reported on July 31 in the Afon Llynfi, a tributary of the River Wye, near Glasbury.

Ann Weedy, Operations Manager for Natural Resources Wales in mid Wales said: "The pollution that struck the Afon Llynfi has had a devastating impact. We are now confident that at least 10,000 fish have died and the wider river life and vegetation has also been impacted. This is not acceptable."

Chemical and biological sample analysis have been returning from the laboratory and more results are expected in the near future

Team members have investigated a number of sites of interest and have spoken to the operators of those sites. Officers have also spoken with local anglers and residents to gain more information to help inform the case.

Ms Weedy added: "We know that local people care deeply about the river and are very upset about the impact this has had on the fish population. We share that concern and getting to the root cause of this incident remains our top priority.

"We also share the sense of impatience in wanting to know what polluted the river and where it came from. We are working as hard as we can and leaving no stone unturned to build up as strong a case as possible for any enforcement action. These things take time and we will provide updates as regularly as possible without jeopardising future enforcement action.

"Not only is the sheer scale of the incident extremely serious, it struck in a Special Area of Conservation which was an important habitat for species including bullhead fish, lamprey and crayfish."

Jenny Phillips, NRW Environment Officer for south Powys said: "Everyone who is working on the investigation has a real passion for the environment; it's why we do our jobs. We are on the ground on a daily basis investigating leads, questioning people of interest and taking samples to be tested in our laboratory.”