SCIENTISTS were today trying to track down the source of the bird flu that has infected thousands of turkeys on a farm in England.

The slaughter of all 159,000 turkeys on the Bernard Matthews farm at Holton, near Halesworth in Suffolk, is due to be completed tonight.

Deputy chief veterinary officer Fred Landeg said only one of the 22 turkey houses on the farm appeared to have been affected, but all the birds were being culled as a precaution.

The animals had come from a hatchery in the UK, none had been moved off the farm and early indications were that this was a recent introduction of disease, he said.

Experts are examining whether there is another origin of the bird flu in poultry, or if it came from wild birds.

The turkeys are infected with the potentially deadly H5N1 strain of bird flu.

Although 164 people have died from H5N1 since January 2003 - mostly in Asia and the Middle East - the Health Protection Agency has reassured the public it is only transmitted through direct contact with poultry.

Officials said the risk posed to humans was "negligible".

There are fears the outbreak may cause sales of poultry to plummet, but health officials said there was no evidence anywhere in the world of the disease being picked up through food.

The officials also said no infected birds had entered the food chain, while supermarkets reassured customers their poultry and egg products were safe.

However, the Government is preparing "very seriously" for the remote possibility the disease could mutate into a form which causes a flu pandemic among humans.

Health Secretary Patricia Hewitt said her department had stockpiled enough Tamiflu anti-virals to cover a quarter of the population, as advised by scientists.

A restriction zone of 800 square miles surrounding the infected farm is being enforced in a bid to contain the virus. 'No panic over park birds'

PEOPLE across Glasgow are being urged not to panic over the latest bird flu outbreak.

Council chiefs are keeping parks open but say visitors should not to have close contact with birds when feeding them.

A council spokesman said: "There is no cause for concern at the moment and we have contingency plans if the situation needs revised."

Fred Landeg, the Deputy Chief Veterinary Officer, said: "I urge bird keepers to be vigilant and to take care if handling birds which appear unwell.

"Owners who suspect disease should quickly consult their vet."

He said that only "extremely close contact" with an infected bird would pose a risk of avian flu passing to humans.

Seven Glasgow parks shut last April after a dead swan was found at Richmond Park - it came after an H5N1-infected swan was found dead in Cellardyke, Fife.