The Government defended the handling of the H5N1 bird flu outbreak today as a cull of thousands of birds continued.
Environment Minister Ben Bradshaw denied there had been a delay in taking action at the Suffolk farm where the potentially deadly H5N1 avian flu strain was found.
Around 159,000 turkeys are being culled at the Bernard Matthews farm in Holton as experts try to find the source of the outbreak.
Mr Bradshaw said: "There were a small number of birds that died on Tuesday and on Wednesday but nothing unusual in a flock of this size. You do get birds dying in those sorts of numbers.
"It wasn't until Thursday, when more than 800 birds died, that the Bernard Matthews vet quite rightly informed the local State Veterinary Service and we immediately put restrictions on that farm. So this idea that there was some delay is simply wrong."
Tests were carried out on Friday, and the strain was identified as H5N1 on Saturday morning when exclusion zones were immediately imposed.
The Cabinet's emergency contingencies committee Cobra is meeting today to discuss the bird flu outbreak.
Government departments, the police, the local authorities, and the state veterinary service will give updates at the meeting.
Mr Bradshaw said he was "satisfied" that everyone had moved as quickly as possible to stem the spread of the disease.
He told Radio 4's Today programme: "The experience of the last year or so in the rest of Europe is that the measures that we have here in our plan - and they are the same in every EU country - have been sufficient to stamp out and contain outbreaks in a single area."
Asked if he could not have imposed exclusion zones as soon as the deaths were reported, Mr Bradshaw replied: "We get reports all the time of suspected bird diseases.
"If we were then to put three or 10-kilometre zones in before we had confirmation, we would put a lot of unnecessary restrictions on a lot of very unhappy farmers."
The Health Protection Agency is taking steps to ensure workers involved with the culling are protected.
Workers at the factory farm have been offered the anti-viral Tamiflu and are being monitored and seen by doctors.
Mr Bradshaw said the source of the infection at the farm was still a "mystery" and a detailed epidemiological survey was under way to try to pinpoint why it might have happened.
A State Veterinary Service spokeswoman said earlier that they had been told the birds were initially diagnosed as suffering from E.coli.
In a statement, Bernard Matthews said today that none of the affected birds had entered the food chain and consumers were not at risk.
"Bernard Matthews continues to work very closely with Defra and other industry bodies," the firm said.
"All proper procedures were followed and we responded accordingly in good time. The company meets and in many cases far exceeds Defra's biosecurity standards for combating avian flu."
Environment Secretary David Miliband cancelled a planned trip to Cumbria and will make a statement on the bird flu outbreak in the Commons this afternoon.
Three major supermarket chains today reported no change in poultry or egg sales following news of the H5N1 outbreak.
Charles Bourns, chairman of the NFU poultry board, said farmers were worried about the potential impact on sales.
He urged shoppers to carry on buying chicken and eggs, saying: "Just keep eating chicken and enjoying it. There is no danger from it. This is a disease of chickens and not of humans."
But Japan temporarily suspended all imports of British poultry following confirmation of the H5N1 strain of bird flu.
The Government said earlier that it was preparing "very seriously" for the remote possibility that the disease could mutate into a form which causes a flu pandemic.
Health Secretary Patricia Hewitt said the risk was "very remote".
"We are preparing very, very seriously and thoroughly for the possibility of a pandemic flu," she said.
The Department of Health has stockpiled enough Tamiflu anti-virals to cover a quarter of the population, as advised by scientists, and conducted a massive preparatory exercise last week.
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 the virus is not transmitted through food.
Defra has set up a restricted area of more than 800 square miles surrounding the farm where the outbreak occurred to try to contain the virus.
The restriction zone, in which poultry must be kept isolated from wild birds and movements must be licensed, covers 806 square miles of east Suffolk and south east Norfolk.
The zone, introduced after consultation with ornithologists, is in addition to the 3km (1.86 miles) protection zone and the 10km surveillance zones already in place.
They will remain in place until further notice, and for at least 21 days.
Birds culled at the affected farm are being transported by lorry in leak-proof containers to a disposal firm in Cheddleton near Leek, Staffordshire.
The firm, called John Pointon & Sons, said the birds are subject to heat treatment to kill all micro-organisms before their remains are incinerated.
Defra's monitoring of wild bird deaths is continuing.