YORK residents have been asked to keep out of the river Foss after a major slurry spill.

Pig slurry entered Farlington Beck, near York, on Wednesday afternoon after what City of York Council said was some "over-zealous muck spreading".

The polluted water made its way into the River Foss, turning part of the watercourse black, and travelled towards York through Sheriff Hutton and Strensall.

Environment Agency officers have been working to contain the slurry spill. They have built an earth dam across the beck to prevent further pollution, and the water behind the dam is being pumped out on to nearby dry land.

They are also using aerators to put oxygen back into the water.

But Agency officers are warning that the incident, which is under investigation, could lead to fish deaths.

Environment management team leader Roger Martin said: "Slurry in the water increases the presence of ammonia, which at high levels, is extremely toxic to fish and other aquatic life. Agency staff are working as quickly as possible to reduce ammonia levels and increase the amount of oxygen in the water, but it is inevitable that fish will die.

"We are alerting people to the fact that they may see dead fish in the River Foss, but we are doing our best to minimise the impact on river wildlife."

An Environment Agency spokesman said it did not know yet how many fish would die as a result of the pollution.

Residents have been asked to avoid the water in the River Foss as it is likely to contain a large number of potentially-harmful bacteria.

Sean Suckling, the council's acting principal environmental protection officer, said: "We're advising people not to come into contact with the contaminated water, and to be sensible about their use of the river area - for example not letting their dogs play in the river.

"It's difficult to tell how long the contamination will last at this stage, but it's likely that the water will be discoloured for several days."

In June thousands of fish were killed in a similar incident when sewage enttered the watercourse at Pocklington.

The sewage spilled into Pocklington Beck when a sewer became blocked. The pollution made its way into Pocklington Canal, devastating the local fish population.

If residents have any concerns about the incident, they should phone the Environment Agency on 0845 9333111.

Updated: 11:14 Friday, August 01, 2003