The clean-up of 12 miles of holiday beaches on the east coast of the island began at the weekend, after vegetable oil was discovered washed ashore.

The blobs are not a threat to public health

The pollution - which comes as families begin their summer holidays - extends between Carmel Head and Point Lynas.

Five-and-a-half tonnes of the substance were found in one bay alone.

The coastguard described the spillage - which is not toxic - as more of a nuisance than a toxic problem.

Scientists are trying to discover how the globules of yellow-white oil came to be washed ashore but this is difficult because of the amount of shipping off the coast.

This is an exceptionally busy shipping area and it may be difficult to identify the offender

Kevin Colcomb, Maritime and Coastguard Agency

Anglesey County Council has launched the operation while samples of the substance are taken to coastguard laboratories in Edinburgh for chemical analysis.

The clean-up, which began at lunchtime on Sunday at Cemaes Bay, will see council contractors use shovels to clear a 30cm-wide band of pollution from the beach.

The Maritime and Coastguard Agency said the oil did not pose a health threat to humans or wildlife and should be cleaned up in 36 hours.

Cemaes Beach had been shut to the public, but re-opened on Sunday afternoon. Meanwhile, other beaches are being assessed.

The yellow swathe of oil is clearly visible

Workers have collected over 100 bags of the substance, which had solidified, and people have begun to return to the beach.

One of the workers said it had started to come ashore on Thursday.

Kevin Colcomb, a scientist with the Maritime and Coastguard Agency, said: "The MCA, the Environment Agency and the local authority are working together to ensure that the impact on local people is kept to a minimum and signs are erected on beaches to warn people of the pollution.

The origin of the spill remains a mystery, however, and an investigation has begun to trace the source.

Mr Colcomb added: "The MCA will be considering traffic routing and cargo along this stretch of coastline.

"However, this is an exceptionally busy shipping area and it may be difficult to identify the offender."

'Impacted heavily'

Holyhead coastguards who found the oil on Saturday morning said the extent of the spill was "substantial."

They were joined by crews from Moelfre, Penmon and Cemaes, as well as the Moelfre Inshore Lifeboat.

Coastguards are confident they can identify the source of the oil when test results are returned in the next few days.

Anglesey council chairman John Williams, who lives in Cemaes, said he did not believe the incident would affect tourism in the area.