More than 200 dead seabirds were discovered across East Lothian 's coast and beaches over the weekend as the cause remains a mystery.
Tests for avian flu are being carried out after hundreds of gannets were washed up onshore in the last couple of weeks.
East Lothian Council said its countryside rangers had reported a further 215 dead birds being found between Friday and Sunday between Yellowcraig beach and Tyninghame.
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The location of the most recent discoveries adds to concerns the birds may be coming from the Bass Rock which has the world's biggest population of northern gannets living on it at this time of year.
However the result of tests which were being carried out on the Rock's population has not been released.
A spokesperson for the local authority said the tests were being overseen by Defra - the UK Government's environment agency - and members of the public are being advised to report any findings of dead birds to the body.
A Defra spokesperson said tests were carried out by the Government's Animal & Plant Health Agency (APHA) on their behalf with results published weekly but "we aren’t able to comment further on individual cases".
The APHA website has cases up to June 7 but does not list any confirmed avian flu in East Lothian, despite the high number of deaths which are now believed to be over 700.
The Scottish Seabird Centre last week confirmed a small number of birds from the Bass Rock population, off North Berwick, had been taken for testing.
Susan Davies, CEO of the seabird centre said that it was too early to tell the severity of the impact on the population if avian flu is confirmed as behind the deaths.
She said: “If avian flu is confirmed, we simply don’t know at this stage how severe an impact it may have on the gannet numbers. We will continue to monitor the situation and update in due course."
Meanwhile dog owners were warned to keep pets away from dead birds, however the local authority stressed that they were not at risk from the avian flu strain if they come into contact.
Instead they said the advice was to avoid spreading the virus which could be carried by dogs who come into close contact.
They said: "Dog owners and walkers are advised to keep dogs under control and to keep their pets away from dead or ailing seabirds that may be encountered on local beaches and coastline which is to minimise the spread of possible avian flu.
"It is in the nature of some dogs to pick up, chew at or even roll on dead wildlife which can mean they can then carry the virus on their coat and paws and so spread the virus to other locations.”
The seabird centre and East Lothian Council urged members of the public not to touch any dead birds they find and to report them to Defra on 03459 335577 or to the Council Ranger service who will collect dead birds from public areas such as beaches.
Any sick or injured birds should be reported to the SSPCA on 03000 999 999.
