A case of "highly pathogenic" bird flu has been confirmed on a poultry farm in Lancashire, the Department for Environment, Food and Rural Affairs said.
The strain of avian flu is the H7N7 strain, which can infect people, but Public Health England has said that the risk to public health from this strain is very low, while the Food Standards Agency said there is no food safety risk for consumers.
A 10 kilometre (six mile) surveillance zone and an inner three kilometre (1.8 mile) protection zone have been put in place around the farm, and humane culling of all birds at the farm is continuing, officials said.
The strain is highly pathogenic, which means it is highly contagious in flocks and can cause deaths in birds.
But it is not the H5N1 strain which has led to hundreds of deaths in people worldwide. Most types of bird flu are harmless to humans but two types - H5N1 and H7N9 - have caused serious concerns.
Other bird flu strains, including H7N7, have infected people, but these have been very rare or have only rarely caused severe illness, experts said.
Chief veterinary officer Nigel Gibbens said: "Final tests results have confirmed a case of avian flu at a farm in Lancashire. Restrictions put in place last week will continue and the humane culling of all birds at the site is progressing.
"These actions are part of our tried and tested approach to dealing with previous outbreaks.
"Public Health England has confirmed that the risk to public health from this strain is very low. The Food Standards Agency has said there is no food safety risk for consumers.
"Bird keepers should remain alert for any signs of disease, report suspect disease to their nearest APHA (Animal and Plant Health Agency) office immediately and ensure they are maintaining good biosecurity on their premises."
Poultry farmers within the 10km zone around the infected premises are not allowed to move poultry, captive birds or other mammals except under licence as a result of the restrictions imposed on Friday when the outbreak was suspected.
In February, a low-severity H7N7 strain of bird flu was confirmed in chickens at a farm in Hampshire. The last highly pathogenic case of avian flu was an outbreak of H5N8 flu in Yorkshire last November, following outbreaks of the same strain on the continent.
Defra said an investigation into the latest outbreak was under way.
The affected premises is in Goosnargh, to the north-east of Preston, and is owned by family business Staveley's Eggs, which produces and packages free range and colony cage eggs.