AN INVESTIGATION has been launched after pools of oil were spotted on a stretch of river in York.

Dog owners have been warned to keep their animals out of the River Foss as Environment Agency officials try to find out where the leak came from.

The oil was seen on Tuesday, floating on the surface of a section of the river which flows through Strensall, and is believed to have come from one of the streams, becks or drainage channels which lead into the Foss.

The agency said its initial investigations had not shown any signs of fish being killed off by the oil spillage, but admitted that the problem was “potentially serious”, although it was not being classed as a severe leak at present.

“A member of our staff was working in the area on Tuesday and saw the oil, so we have been assessing the situation since then and believe we have traced it back to one of the Foss’s tributaries,” said an Environment Agency spokesman.

“We have some ideas about where the oil may have come from, although it is too early to say for certain at the moment.

“We have installed a boom at the mouth of one of the tributaries in the Strensall area to hold back any of the oil and prevent more of it getting into the River Foss. It appears that quite a lot of the river in this particular area is affected and that makes it a potentially serious spillage.

“Our advice is for people to stay out of the river and make sure their dogs do not go into the water as well.”

One dog walker from Strensall, who did not wish to be named, said he had seen the oil glinting in the sunlight on Tuesday evening.

“There was a film covering the river and a chemical smell, so it seems like it must be something like diesel.

“Water voles were swimming through it and fish were coming to the surface, and the river absolutely reeked of chemicals.

“It’s the first time I’ve seen anything as bad as this on the river and it must be pretty serious – it needs to be dealt with quickly to avoid it becoming a real environmental threat.”