This is the second pollution incident in the Dee system

Initial estimates suggest up to 150,000 young salmon, out of 300,000 at the hatchery, have been killed.

The salmon have been reared in tanks and were eventually due to be fed into the River Dee catchment to replenish stocks.

The River Ceirw is a tributary of the Dee but the Environment Agency have insisted there is no evidence of pollution in the main river and no dead fish have been found.

The agency have conducted an investigation and are satisfied they have found the cause of the pollution - subject to confirmation from laboratory tests.

The main fish kill started last Tuesday night but fish have still been dying every day

Hatchery Manager, Doug Jones

The agency's John Rowlands said: "We now believe that we have identified the source of the pollution and on going inquires are continuing and a prosecution could follow."

While the pollution has dealt a hammer blow to the project, staff have said they are hopeful the remaining stocks can be saved.

Hatchery Manager, Doug Jones, said: "It is an absolute disaster what has happened.

"Up to 150,000 juvenile fish have been killed and around 10 adult salmon and sea trout.

"The main fish kill started last Tuesday night but fish have still been dying every day.

"It is believed that chemicals got into the nearby the Ceirw River that supplies the hatchery with water."

Significant impact

This is the second major fish kill on the Dee system.

In July 2000 an estimated 100,000 coarse fish, and 200 salmon were killed in the Bangor on Dee area.

At the time of the incident officials believed it would take years for the fish stocks to recover from the disaster.

The agency have said that this latest incident will have a significant impact on stocks of juvenile fish.

They said the pollution has also depleted the adult stock fish which provide the future fish population for the rivers Dee, Alwen and Tryweryn.