More dead seabirds covered in a sticky, oily substance have been found along the south coast of England.
The RSPCA said 200 birds were found dead at Chesil Beach in Dorset on Friday and another 162 were rescued. Around 100 were rescued and 15 were found dead the previous day.
Thousands of seabirds have been washed to shore along the south coast between Cornwall and West Sussex.
Wildlife staff expect to see more guillemots and razorbills come ashore over the weekend. The birds are unable to clean themselves.
The substance on their feathers has been identified as a refined mineral oil by scientists at the Environment Agency.
The BBC reports the oil, a colourless, odourless substance which is related to petroleum jelly, may have been discharged into the sea accidentally or deliberately. It was earlier thought to be palm oil.
The RSPCA is treating the birds at the West Hatch animal centre in Taunton using margarine and washing up liquid to clean the substance from their feathers. Manager Peter Venn said:
"What we are hearing are reports of birds showing up on the Sussex coast, so that may mean that the weather is pushing them more easterly.
"Everything is certainly not over by any means. There were quite a lot of birds dead in the water this morning. What we don't know is what is still out there."
The BBC reports the numbers of dead birds are as yet unclear.
A coastguard plane has been searching the sea between Dover and the Isles of Scilly for the source of the pollution.