FOUR young swans have been plucked from an oil-covered lake in an emergency operation.

Booms have been installed on Hemlington Lake, on the edge of Middlesbrough, while investigations continue into the source of the pollution.

Environment Agency inspectors believe engine oil was poured down a nearby drain, which then ran into Bluebell Beck and into the lake.

Reed beds were also damaged and small fish and wildfowl are at risk.

The four cygnets removed by RSPCA inspectors have been taken to a specialist animal hospital in Norfolk.

An Environment Agency spokesman said: "We don't think there is a huge amount of it, but it has formed a slick about 25 metres by three metres on the lake.

"It will probably take one or two days to clear and we will need to monitor the situation to make sure the oil has stopped passing through. It is obviously a serious thing to do, to pour engine oil or any other pollutant down the drain.

"It has to be disposed of properly, otherwise it ends up polluting the water and causing serious damage."

A spokesman for Middlesbrough Council said: "It is a great pity that a moment's thoughtlessness has caused such a lot of damage and such a lot of expense for a lot of agencies."

RSPCA inspectors will continue to monitor other wildlife, such as moorhens and ducks, which have also been affected by the spillage.

A spokeswoman for the RSPCA said: "We had to leave two parents on the site and we have taken the four juveniles to East Winch Wildlife Hospital in Norfolk, which specialises in rehabilitation. Hopefully, we will be able to get them back in the next few days.

"There have been lots of moorhens and ducks, but we can't contain them because it is very hard to catch them.

"The parent swans are not in immediate danger - they are bigger and stronger birds.

"It is very frustrating. We should be privileged to have wonderful nature and places to go and look at wildlife and it is unfortunate for everyone they should be contaminated in this way."