Preliminary tests have confirmed the H5 avian flu virus in a sample from a swan found dead in Central Scotland, local health officials said yesterday.

A statement from the Scottish Executive said tests had found the "highly pathogenic H5 avian flu" in a sample from a swan founddead in the Cellardyke area of Fife.

The exact virus strain is not yet known, but tests were continuing and further results were expected on Thursday, said the Scottish Executive.

The Cellardyke area has been sealed off. If the virus is confirmed as the deadly H5N1 strain, there may be further restrictions put in place.

A protection zone of a minimum of three kilometers radius and a surveillance zone of 10 kilometers will be established while bird keepers in the protection zone are being instructed to isolate their birds from wild birds by taking them indoors.

Measures to restrict the movement of poultry, eggs and poultry products from these zones will be brought into effect immediately.

The H5N1 virus does not at present pose a large-scale threat to humans, as it cannot pass easily from one person to another.

However, 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.

According to the National Farmers Union Scotland, the Scottish poultry industry produces 127,000 tones of meat and 740 million eggs. No poultry farms are believed to be operating in the immediate area where the bird flu case occurred.