The Environment Agency Wales has set up an incident room after thousands of river fish were killed in two separate incidents.

A thousand brown trout were killed in the River Syfynwy in Pembrokeshire on Thursday and 5,000 salmon and trout in the River Tawe near Ystradgynlais in south east Wales on Friday.

Pollution blamed

The deaths have all been blamed on pollution entering the rivers.

Scientists are analysing the fish and water samples in the Agency's laboratory.

In Ystradgynlais, investigations are being centred on a two kilometre stretch of the River Tawe in the Swansea Valley near an industrial estate.

Angler Geoff Williams: "Every pool had scores of dead fish"

Geoff Williams, the secretary of the Tawe and Tributaries Angling Association, said: "I walked the river on Friday, and literally every pool had scores of dead fish, both adults and juveniles.

"It is very very difficult to speculate, but I would have thought that it was some kind of gill irritant because when I saw the fish they were leaping clear of the water as if they were trying to get oxygen," he said.

Mr Williams said he thought the Environment Agency did a very good job in difficult circumstances, but that forthcoming grant cuts may mean that it can employ fewer wardens to prevent pollution incidents.

Legal action

Paul Edmonds, incident co-ordinator for the Environment Agency, said evidence was being collected with a view to possible legal action.

"We have identified the possible source of the pollution and we will continue our investigations to confirm that our suspicions are correct," he added.

Extensive checks have shown that the polluting discharge has now stopped.

Flows of water were said to have helped dilute the substance as it made its way down river.

A passer-by first raised the alarm after spotting several dead fish, mostly juvenile trout and salmon, on the surface of the Tawe.

Environment protection officers have urged the public not to remove any dead fish from the river.