A "SIGNIFICANT" number of fish were killed in a river pollution incident in Caerphilly county borough this week.

Environment officers from Natural Resources Wales are invesitgating the pollution incident at a mile-long stretch of Nant Cylla, a tributary of the River Rhymney.

They said the incident caused "significant fish kill" on Monday, March 21.

Officers attended the site shortly after receiving reports of "discolouration and froth" in the water.

There, they collected samples and discovered more than 300 fish had been killed, including brown trout and sticklebacks.

The environment agency has since been able to identify the source of the pollution and to confirm that leaks into the watercourse have since stopped.

The samples taken will now be analysed and will inform officers' next course of action.

"Protecting Wales’ rivers and the communities and wildlife that depend on them is an important part of the work that we do," said the agency's operations manager, Jon Goldsworthy. "As soon as we received reports of this incident, our officers were out on site to investigate.

"Unfortunately, we can confirm that over 300 fish have been killed in this pollution incident, which will have a significant impact on local fish stocks.

"We believe we have found the source and we’ll consider what action to take next, including any appropriate enforcement action to be taken against those responsible.

"We’re grateful to those who reported this incident to us. We would encourage anyone to report signs of pollution to us on 0300 065 3000, or via our website to ensure we can respond as swiftly as possible."