BBC News | Wednesday, 5 April 2006

Exercise Hawthorn was halted by Chief Veterinary Officer Debby Reynolds.

She said the decision would divert all resources to the situation in Scotland, adding officials were "already in a high state of readiness".

Preliminary tests have found the H5 virus in a sample from the swan but the exact strain is not yet known.

Ms Reynolds said she had "every confidence that officials north and south of the border will work together to manage this incident successfully".

Hundreds of vets and farmers were taking part in Exercise Hawthorn, an office-based initiative set three days into a hypothetical outbreak of avian influenza in poultry.

The Department for Environment, Food and Rural Affairs in London was running it with control centres in Bury St Edmunds, Leeds, Cardiff and Gloucester.

The exercise was checking safeguards are enough to prevent an epidemic.

Farm 'outbreak'

It also involved the Association of Chief Police Officers, the Environment Agency, Downing Street, the Ministry of Defence, and other government departments.

Veterinary and farming groups were among the dozens of other organisations involved, also including groups from the shooting and pigeon-racing sectors.

Animal welfare charity the RSPCA, the EU, and foreign governments also took part.

The exercise was based on a scenario in which bird flu was found on a free-range poultry farm in Norfolk, with suspected cases at a turkey farm in the north of England and at an egg production unit in south Wales.

Last October, a similar test focused on making sure the necessary IT facilities were in place.