About 35,000 Gressingham ducks will be culled after a bird flu outbreak at a poultry farm near Diss.
Gressingham Foods, the UK's largest duck producer, has confirmed that a highly-pathogenic strain of avian influenza has infected a flock run by its supplier Green Label Poultry at Redgrave, close to the Norfolk/Suffolk border.
It is the latest in a series of outbreaks across the country.
A company statement says a bird flu case in a "local back-yard flock" during the weekend had put many of the firm's facilities inside control zones, adding: "In addition to this unfortunately a Green Label duck farm was confirmed as having highly pathogenic avian influenza.
"Since the weekend the farm has taken every precaution and there has been no movement of birds or other material off the premises, the farm is now under APHA (Animal and Plant Health Agency) control.
"The welfare of our birds is an absolute priority, and we work to the highest standards in hygiene, bio-security and animal welfare across all our farms."
A 3km Protection Zone - enforcing additional biosecurity and movement controls for poultry keepers - and a 10km Surveillance Zone has been put in place around the site.
Defra said: "All birds on the infected premises will be humanely culled."
It is the second outbreak in the area this week, after a case was confirmed at a site near Elmswell, near Bury St Edmunds, on February 26.
Across the country, more than 80 cases have been recorded this winter during the largest outbreak of bird flu the country has ever seen.
They have also included cases at a farm at Pentney, near King's Lynn, in a small domestic flock at a residential property on the Holkham estate, and at Pensthorpe Natural Park near Fakenham.
Health agencies advise that although avian influenza is devastating to bird flocks, the risk to human health and food safety is very low.
To halt the spread of the disease, all captive birds - including commercial and pet poultry flocks - have been required to be kept indoors since an Avian Influenza Protection Zone (AIPZ) was enforced across the country in October.
Dead wild birds should be reported to Defra’s helpline on 03459 33 55 77 and poultry keepers should report signs of disease to APHA on 03000 200 301.
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