Northumbrian Water has been fined £12,000 for polluting a County Durham river and killing more than 1,000 fish.

The company pleaded guilty to allowing untreated sewage to leak into the River Gaunless, near Bishop Auckland, in June last year.

It also admitted to three other charges of pollution, two dating July last year and one from last November. These three charges were seen as minor incidents.

Around 500 trout and at least another 500 water course fish such as bullhead, stone loach and minnows were killed in a 2km stretch of river downstream from South Church where the River Gaunless meets the River Wear in the incident last June.

Bishop Auckland Magistrates were told that the pollution was down to the mechanical failure of a mechanism inside the sewage overflow system.

Paul Kelly for Northumbrian Water told the court the company had reacted to the situation immediately and the mechanism had since been replaced and upgraded.

He said the incident could not have been forseen and everything possible had been done to put the damage right.