SIX distressed seabirds covered in a white waxy substance washed up on Bournemouth beaches on Friday.
Today, the RSPB has said those responsible should be shamed and potentially prosecuted.
On Saturday afternoon Dorset Wildlife Trust said around 20 birds had been rescued in the morning, while 20 had been found dead.
It said 30 birds were found at Swanage yesterday and there were reports of more washing in at Swanage today.
Marc Smith, from Dorset Wildlife Trust, said: “Our concern now is that the wind has changed direction which will start pushing the birds out to sea.
"As the days go on the birds will become colder and more exhausted, lowering their chances of survival. Birds may start to wash up in different areas now because of this wind change.
"If you see birds in your area please report this to the RSPCA who are leading the rescue effort.
"We know the public are keen to help but we strongly advise they do not try to rescue the birds. We do not want anyone putting themselves in danger and if the birds are not handled correctly they can end up exhausted which reduces their chance of survival.
"The number of birds is staggering and there is a wider concern of the long term impact this could potentially have on the marine environment as a whole. Dorset’s coastline is rich in marine wildlife including dolphins, sharks and seals.
"Chesil Cove, the area where most of the birds have washed up, is part of a newly proposed Marine Protected Area. Home to starfish, brittlestars, queen scallops, burrowing anemones and the rare pink sea.
"We do not know if this substance will enter the food chain or if other animals are being affected. Only time will tell what the long term effects of this environmental disaster will be.”
Two kittiwakes, one cormorant, two razorbills and one guillemot are being looked after by wildlife specialists after washing up in Bournemouth on Friday, while a further two razorbills were recovered from the sea at Swanage.
Some birds were also discovered at Christchurch beaches on Friday night.
Further west, at Chesil Cove, the RSPCA has rescued more than 120 birds since reports of dead seabirds washing up first started to emerge on Thursday.
Dorset Wildlife Trust marine conservation officer Emma Rance told the Daily Echo: “We’ve collected a couple of black sacks full of dead birds at Chesil Cove. Sadly, a juvenile puffin was among them. A number of birds have also washed up dead at Kimmeridge Bay.”
The seabirds are mainly guillemots, but other species are affected.
Samples of the substance have been collected by the RSPCA and the Environment Agency and sent for further analysis. Scientists are, so far, unsure exactly what it is.
Durlston Country Park coastal marine ranger Ben Wallbridge said: “We are working closely with the RSPCA to monitor the situation. We’ve had reports of these two birds in the water at Swanage. They are alive but we are waiting for conditions to improve before trying to retrieve them.”
The RSPCA said the birds had not initially responded well to the usual methods of removing oil.
Ms Rance said: “Until we get back the results, we cannot really speculate on what this substance is. It is very sticky, white in colour and odourless. It is certainly something I’ve never seen on birds washing up in Dorset before.”
BBC wildlife presenter Chris Packham said: “What’s particularly frightening is that if you’re picking up a hundred on the beach, there could be very many more which have died and been lost at sea.
“So this could be a tip of an iceberg as it stands at the moment.”
DWT staff say the oil has been coming off by using a combination of water and margarine.
Those responsible for a spill that could have caused the deaths of hundreds of sea birds along England's south coast could be prosecuted, wildlife experts said on Saturday.
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.
Conservationists 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 and they have ruled out palm oil.
Tony Whitehead, from the RSPB, said investigations were continuing to establish what it was and where it came from.
''It's a refined mineral oil, which is a colourless and odourless substance, and it's related to petroleum jelly,'' he said.
''We don't know where it came from and we need to do a lot more testing on this substance to try and track it back to its source.
''There are people speculating it could be from a ship, that's possible but we just don't know yet.
''We need to look at what happened and if appropriate take legal action and also, frankly, shame the people.''