A fish kill on a tributary of the Callan River in County Armagh is “probably the worst ever” in the area, local anglers have said.

It is thought hundreds of juvenile salmon have died as a result of a slurry spill at the Corkley River near Keady.

The incident was first reported to the Northern Ireland Environment Agency (NIEA) on Saturday 21 October.

Officials have visited the area and the dead fish are being counted.

Up to a mile-long stretch of the river is believed to have been affected.

A spokesperson from the NIEA said a source has been identified and statutory samples have been collected.

The Callan is a tributary of the Blackwater, one of the main rivers flowing into Lough Neagh.

As the pollution travels downstream, it will become more diluted as the distance increases, ultimately disappearing.

At this time of year, salmon and brown trout are coming into the river system to breed.

As well as fish, the invertebrates, insects, worms and larvae, that they feed on have also been affected.

Armagh Angling Club described the incident as a blow from which it could take years for the fish stocks to recover.

Local environmental conservation group Friends of the Callan River have said the deaths of “hundreds” of fish was devastating.