Hunt for Strait's oil leak source

The source of the oil leak is still being investigated

Investigations are continuing to find out who was responsible for an oil spill which polluted a large stretch of the Menai Strait.

The five-mile (8km) slick was spotted on Sunday by sailors in the Menai Strait which separates Anglesey from the mainland.

The coastguard said the immediate source had been identified as a leaking pipe, which had now been sealed.

Officials are investigating whether the escape was caused by vandalism.

Meanwhile, coastguards are warning people and craft to stay out of the water.

"The Environment Agency is investigating this morning but they've stopped the source. We believe that most of it has been dispersed," a spokesman said.

Clean-up workers try to block a pipe leading to the water

The oil - much of which has now been dispersed - entered the water south of Caernarfon and spread right up the coast as far as the Britannia Bridge.

It was said to be made up of a number of industrial oils including diesel, generator fluid and heating oil and is thought to have come from an outfall pipe.

'Environmentally sensitive'

In some of the worst affected areas, people are cleaning up the remnants of the slick from the shore line but officials hope the rest will disperse on its own without need for a chemical clean-up.

The Menai Strait is considered to be an environmentally sensitive area for wildlife with its tidal mud flats being an important feeding ground for birds with oyster catchers and curlew land making it a popular spot for bird watchers.

Mike Willis from the Countryside Council for Wales said the damage still had to be evaluated.

As the day went on we got more and more black stuff and heavy oil left on the beach Alan Williams, watersports centre

"We're lucky it was this time of the year, because in the winter there would have been lots of birds," he said.

"The marine interests of the Straits are of international importance, because of the quantity of oil released I don't think it's going to have much of an impact."

He added that there was concern for shell fisheries in the area, but that people with commercial interests in the Straits had been alerted.

The Welsh National Watersports Centre based at Plas-Menai suspended all activates on Sunday following the sighting of the oil slick.

Alan Williams, manager of the centre, said: "As the day went on we got more and more black stuff and heavy oil left on the beach."

He described the beach near the centre as being mottled with black spots of oil and said people in the area had been mopping up.

"Earlier on there was light oil on the surface of the water. Later on we started getting heavier black oil in globules," he added.