Officers from Natural Resources Wales (NRW) have been dealing with a pollution incident in a tributary of the river Aeron near Cilcennin in Ceredigion.
The incident was reported on Friday (19 April) and officers attending the site at the weekend confirmed that a small number of dead fish had been found.
NRW Officers have identified a possible source of the pollution and are providing advice to prevent this from happening again.
The source identified is not slurry or agricultural. Officers have taken water samples and continue to investigate the impact of the incident.
Callum Stone, Environmental Officer for Natural Resources Wales, said:
“Protecting Wales’ rivers, along with the plants and wildlife that inhabit them is one of our biggest priorities.
"If you have any information regarding the incident or see any fish in distress please report it to our incident hotline on 0300 065 3000.”