Increasing numbers of birds are washing up on the south coast after being covered in a mysterious substance.
Wildlife experts are no closer to discovering the cause of the environmental damage, which has seen more than 100 seabirds taken into care at the RSPCA West Hatch wildlife centre in Taunton, Somerset, since yesterday.
Most of the birds, guillemots, were found at Chesil Beach, near Portland in Dorset. One bird was found alive as far as Worthing in west Sussex, and is now being cared for at a veterinary surgery. Another, found in the Isle of Wight, is now at a local animal rescue centre.
Around 200 miles of the English coastline is being investigated. The Environment Agency has taken samples of the water for testing.
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 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."
The Maritime and Coastguard Agency (MCA) is waiting to hear from the Environment Agency later today in order to discover the possible cause of the pollution.
A spokesman said: "The MCA is regularly called upon to react to a wide range of maritime incidents and to develop a comprehensive response procedure to deal with any emergency at sea that causes pollution or threatens to cause pollution.
"This occurrence of seabirds being washed up on south coast beaches contaminated with a product is rare. We are working with partner organisations and agencies to deal with this event.
"The Environment Agency has taken samples of the product and is currently analysing it to identify it.
"The RSPCA and RSPB are collecting data and the contaminated birds are being cleaned at the RSPCA West Hatch Wildlife Centre in Somerset.
"We will continue to monitor this situation and await the results of the analysis of the product."
An RSPCA spokesman said they were pleased with the public's willingness to help the stricken birds, but warned of the dangers involved.
The spokesman said: "We would urge people to be cautious going down to the coastline affected.
"The instinctive reaction is to go down and look, or to help out. But we don't know what this substance is, so our message is for people - especially those taking dogs down to the coastline - to please be careful."
The RSPCA centre at West Hatch took in 139 birds yesterday, but said 16 of those died.
This morning the centre received another 23 birds and has about 20 more to come in from Hampshire.
Staff at the wildlife centre have been treating the birds, which are now recovering in cages and have been fed fresh fish.
West Hatch manager Peter Venn said: "The current situation seems to be that the numbers of the birds coming in to us may have peaked for the time being, but that may change.
"The objective now is to work with the birds that we have in care and try to ensure we can do the best for them through the rehabilitation process.
"It does seem there are less birds coming off the beach today than there were yesterday, but if the weather changes this could also change."
Supervisor Paul Oaten has been cleaning the birds in the centre's dedicated cleaning room using vegetable oil and margarine, followed by washing detergent.
"So far the birds have been in the holding room in their individual boxes and the birds that have been deemed fit enough and bright enough to wash have had margarine massaged into the areas of feathering where this very sticky contaminant is," he said.
"We've left that for half an hour, maybe a little bit more, to break down the contaminant and now what we are doing is putting them through our usual wash process with washing detergent.
"They're coming up very well. There's a couple of little patches that haven't proofed, where the water beads off the feathers, but we will do these birds in two washes, so we do a pre-clean to get the 99% off and then a final clean to get them 100% clean."
Mr Oaten said that while they still do not know what the contaminant is, they are using a process known to clear sticky substances in order to do the best for the birds.
RSPCA animal collection officer Steve Powell, 61, has been working with oiled birds for 25 years and took 23 birds in to West Hatch this morning.
"It initially started on Tuesday and has gradually increased on each day," he said.
"Today I went down to Portland, which seems to be the main area, at Chesil Cove, where they are coming in.
"I met a colleague there who had been collecting them with quite a few volunteers.
"We saw quite a few birds waiting to be collected. They were just waiting for the tide to go out, but there were also a number of dead ones, unfortunately.
"The ones we've brought in today are a lot thinner than the ones we first collected on Tuesday. Whether they have been fighting at sea against the pollution, or how long they have been out there without feeding, I don't know. They are quite lively, but also quite thin.
"They do say that for every live bird that is taken off the beach there are probably nine others that have died at sea."