AN investigation has been launched after thousands of dead fish were found in the River Skerne.

Residents are being warned not to let their children or dogs play in the water in case it is polluted.

The Environment Agency was alerted to the problem by members of the public at 1.30pm yesterday and three environmental officers were sent to the scene.

Samples have been taken from the river, at intervals along a three to four kilometre stretch between Newton Aycliffe and Darlington, and were being sent off for analysis today.

The agency confirmed they were treating this as a serious "category one incident".

Spokeswoman Louise Turner said: "This incident is what we call an extensive fish kill, as thousands of fish, including trout, have been found dead.

"When there has been a period of hot weather, it can cause problems of this nature, but this is unlikely in this case due to its scale. Instead, we are investigating the possibility of a pollutant in the water."

The agency said it was aware that Northumbria Water had been working in the area, but at this stage, did not believe the two were related.

The majority of the dead fish have been found near Newton Aycliffe Industrial Estate.

Ms Turner said that within a 100-metre stretch of the river, near the Hallgarth Road Bridge, in Newton Aycliffe, more than 1,000 dead fish had been found.

She added: "Samples have been sent off to one of our specialist labs for analysis, though it may take a few days before we find out what has caused this.

"We are still at the very early stages of this investigation."

Last night, Darlington Borough Council was erecting signs along the river bank warning residents not to let their children or dogs go into the water.

A council spokesman said: "This has come at a very bad time, especially as the schools are breaking up for the summer holidays and rivers do attract children.

"We would always ask children not to play in rivers, due to the safety risk they pose at all times, but we are making a fresh appeal in the light of this news.

"We urge children to stay away and for people to keep dogs on their leads. If children want a swim, they should visit a pool, like The Dolphin Centre, where they will be safe."