Restrictions on the movement of poultry were in force last night after three mute swans tested positive for the deadly H5N1 strain of bird flu.
The dead birds were found on the Abbotsbury Swannery, an open reserve in the Chesil Beach area of Dorset, during routine surveillance. The Health Protection Agency (HPA) is monitoring about 12 staff at the reserve for signs of the disease, though the risk of infection is said to be low.
John Houston, general manager at Abbotsbury Tourism Ltd, said the birds were found by a member of staff at the swannery. The Department for the Environment, Food and Rural Affairs (Defra) was notified.
"Our main concern is the welfare of the swans, our staff and the general public," Mr Houston said.
"We are working closely with Defra to ensure that this outbreak is contained and that the number of swans affected is limited."
Mr Houston said the HPA advised there was almost no risk of infection among swannery staff but they had begun a course of Tamiflu tablets as a precaution.
Three of the staff are full-time, while the others were identified as coming into contact with the swannery for different reasons, including deliveries.
Defra has set up control and monitoring areas around the site to try to contain the outbreak. Severe movement restrictions apply within the zones, with bird owners only permitted to move their flocks under special licence from Defra.
The control area extends approximately 15 miles to the south-east of Abbotsbury, and includes the town of Weymouth, Chesil Beach and the Portland Bill headland, while the larger monitoring area of some 20 miles also covers the town of Dorchester.
Within the control and monitoring areas, bird gatherings such as poultry auctions and pigeon races are banned, and owners of poultry and other captive birds are required to house their flocks where possible.
Hunting wild birds and releasing game birds is also banned. Commercial poultry farms will be inspected.