Health experts are carrying out more tests on a swan found dead in Scotland that tested positive for bird flu.
The EU's bird flu laboratory in Surrey is expected to confirm the UK has its first case in a wild bird of the H5N1 strain, blamed for human deaths.
A 1.8-mile (3km) protection zone to prevent poultry being moved is in place around Cellardyke in Fife, where the bird was found eight days ago.
The government's national emergency committee has met to discuss the issue.
The Scottish Executive said further restrictions may be put in place if the strain is found to be H5N1, but officials stressed there was no reason for public health concern.
Scotland's Chief Veterinary Officer Charles Milne told a media conference the bird - thought to be a mute swan, a native UK breed - was collected the day after it was reported.
But he defended the programme set up to deal with bird flu several months ago.
"The timelines could not have been tighter in my opinion," he said. "We got the results at the earliest possible opportunity and the appropriate measures were put in place."
Initial tests show the swan was carrying a form of the H5 avian flu virus - but the exact virus strain is not known.
The H5N1 virus does not at present pose a large-scale threat to humans, as it cannot pass easily from one person to another.
But experts fear the virus could mutate to gain this ability, and in its new form trigger a flu pandemic, potentially putting millions of human lives at risk.
Prime Minister Tony Blair said it was important for people to realise that "this is not a human-to-human virus, it is something that is transmitted to poultry".
"It is only if humans are in direct and very intensive contact with poultry that there is any risk involved."
The H5N1 virus has appeared in birds held in quarantine in the UK.
The virus was found in Taiwanese finches at a secure animal unit in Essex in October.
The decomposed body of the swan was taken away for tests on 30 March after being found on the slipway of the village's harbour.
Locals reportedly spotted the dead bird floating around in the water for several days with one women saying she had seen seagulls pecking at it.
The resident who found the dead swan washed on the shore at the pier told BBC Scotland she was concerned over an apparent lack of urgency shown by the authorities.
"When I found the dead bird, I called the police, who told me to phone the SSPCA, who in turn told me to phone Defra," said Tina Briscow, 68.
"It was over 12 hours later when someone came to collect the bird."
Scotland's Chief Veterinary Officer said the dead swan was decomposed and appeared to have been partially eaten.
Amid concern the flu could spread to pets, Mr Milne said there is no evidence that the "predation" was by domestic animals.
BIRD FLU FACTFILE
Bird flu viruses have 16 H subtypes and nine N subtypes.
Four types of the virus are known to infect humans - H5N1, H7N3, H7N7 and H9N2
Most lead to minor symptoms, apart from H5N1
H5N1 has caused more than 100 deaths in Cambodia, China, Indonesia, Thailand, Turkey and Vietnam
The World Health Organisation says not all H5 or H7 strains are severe, but their ability to mutate means their presence is "always a cause for concern"
He said the public should report any sightings of dead wild birds.
However, Mr Milne said the countryside "remained open".
Microbiologist Professor Hugh Pennington told the BBC there was no health risk from eating properly cooked poultry or eggs.
He said: "It's not eating the flesh or eating eggs that is the problem.
"It's contact with sick or dying or recently dead birds that's the issue - so the public is not at risk; the birds are."
The nearest poultry farm was on the boundary of the surveillance zone and much of the birds in Fife were indoors, the Scottish Farmers Union said.
In Europe, the H5N1 strain has already been found in countries including Denmark, France, Germany, Italy, Poland, Serbia-Montenegro and Switzerland and measures have been taken to try to prevent its spread from wild birds to poultry.
The swan was found in Cellardyke harbour a week ago
Dr David Nabarro, the United Nations' bird flu co-ordinator said until the strain of bird flu had been identified, the advice to governments was to behave as though it was H5N1.
"I can't tell you at this stage how likely this is to be H5N1, but I think it's prudent for the government to be behaving as though it is, and therefore to be introducing the necessary precautions," he said.
Representatives from Defra, the Scottish Executive, the Department of Health, the Cabinet Office and 10 Downing Street attended the meeting of the government's national emergency committee, Cobra.
"The meeting reviewed the contingency plans that are already in place and concluded that all relevant steps are being taken," the Cabinet Office said.
The government advises that if you find one or more dead swans, ducks or geese, more than three dead birds of the same species or more than five dead birds of different species, in the same place, you should contact the Defra helpline on 08459 33 55 77.