An illegal dumping of cargo oil at sea could have caused the deaths of hundreds of sea birds along England's south coast, an expert said.
Thousands of birds have been washed to shore along coastline that stretches from West Sussex to Cornwall after being covered in a sticky, oily substance.
Wildlife experts and volunteers raced to the shoreline to save as many birds as possible, and hundreds - mostly guillemots - are now being treated at RSPCA centres.
Scientists from the Environment Agency identified the mystery substance as a refined mineral oil, but not from an animal or vegetable-based oil.
Some kind of accident such as a leaky gearbox or a broken pipe is the most likely cause of a mineral oil spill, but it is unusual that it would cause this much havoc.
So that makes one think it could be an illegal dump of cargo oil - oil that is being transported rather than used in the working of the ship.
This could happen if there was illegal washing out of tanks at sea. Some unscrupulous operators, and they are rare, flush the tanks out there because it is cheaper and easier than doing it in dock. It is illegal and quite harmful.
RSPCA volunteers have been scouring the coast in Dorset for more birds covered in a mysterious sticky substance.
Workers are racing against time to remove a glue-like material trapped to the feathers of hundreds of birds washed up on the south west coast. Hundreds of washed up birds have died, as a result of the mystery substance, according to the RSCPA.
An investigation is underway along 200 miles of coastline. ITV News Reporter Richard Lawrence reports from an RSPCA centre near Taunton:
Hundreds of sea birds are feared dead as many are washed up along the south coast. Covered in oil - there are concerns hundreds more could die over the coming days.
Increasing numbers of seabirds are washing up on the south coast covered in a mystery substance.
Wildlife experts are no closer to discovering the cause of the environmental damage, which has seen more than 100 birds taken into the RSPCA West Hatch wildlife centre in Taunton, Somerset. Most of the birds were found at Chesil Beach, Dorset:
RSPCA deputy chief inspector John Pollock, who has been leading the rescue mission in Dorset, said
We just do not know what this substance is. It is white, odourless and globular, like a silicone sealer. The best way I can think to describe it is 'sticky Vaseline'.
The numbers of the birds coming in have been growing and sadly there were quite a few dead birds this morning.
We are still down at the beach, though, collecting and trying to save as many of them as we can. We are expecting this rescue mission to continue through the weekend.
A rescue operation is under way after approximately 100 seabirds were washed up on the south coast covered in an unidentified sticky white substance.
The RSPB said the guillemots, a kind of awk, were discovered on Lyme Bay near Weymouth.The birds have been taken to West Hatch Animal Centre in Taunton but attempts to clean them have been hampered by not knowing what the substance is, Grahame Madge, of the RSPB, said.
Hundreds of seabirds have been washed up on the south west coast, covered in an unidentified sticky substance and causing the RSPCA being called to the rescue.
Guillemots have been found along the Dorset and Devon coast between Weymouth and Torquay. Many have sore legs and are covered in a greasy film.
The birds are being transported to the RSPCA's West Hatch Wildlife Centre in Somerset, where efforts are being made to clean them. Early signs are that they are not responding well.
An RSPCA manager has said it is "too early" to assess how successful the organisation's attempts to help the 100 guillemots washed up on the south west coast will be.
Peter Venn, RSPCA West Hatch manager, said:
The numbers of birds arriving in to our centre are growing and we are doing all we can to help them - but it is too early to tell how successful these attempts will be.
We do not know what this substance is or where it has come from yet but we do know it is not fuel. It may be bi-product from manufacture, but at this stage we just do not know.
We would urge anyone who finds any of these birds to contact the RSPCA on 0300 1234 999.
There are also reports of the sticky substance washing up on the beach, so we would urge people walking their dogs in the area to also be careful.
There is worrying evidence that more of Britain's native bird population is dying out.
A group of conservationists say the UK has been losing an average of one breeding pair every minute since 1966.
The species worst affected by the decline are House Sparrows and Wrens.
ITV News' West of England Correspondent Emily Morgan reports on what is behind the alarming decline:
Thousands of migrating birds have been dying before reaching England this week because of an appalling combination of fog and winds around the coast, according to the Royal Society for the Protection of Birds (RSPB).
Some fishermen have told the charity of the deaths of many exhausted and disorientated "garden" birds plunging into the sea around their vessels, a spokesman said.
England's east coast, from Northumberland to Kent, has seen the arrival of many birds, including redwings, fieldfares, bramblings and blackbirds, perhaps numbering in their millions.