Turkey meat imported from Hungary was the most likely cause of the bird flu outbreak at a Bernard Matthews turkey plant in Suffolk, according to a report from the Department for the Environment, Food and Rural Affairs (Defra).
Defra has confirmed that there is no evidence that the meat suppller broke any rules.
An interim report said that of the two possible hypotheses for the introduction of H5N1 into the poultry plant, there is "little evidence" of transmission from a wild bird source.
The theory that the virus spread from imported poultry products from Hungary is supported by tests carried out at the Veterinary Laboratories Agency (VLA) confirming that the virus strain found in poultry in Suffolk is "essentially identical" to that which caused the outbreaks in Hungary. The report concludes that this is "currently the most plausible" route of transmission.
Defra confirmed:
• There is no evidence that any meat entered the UK food chain from the restricted zones in Hungary;
• From evidence gathered by the Food Standards Agency (FSA) investigation team, it appears that all food importing and processing activities being undertaken at the Bernard Matthews Factory at Holton are in line with EC law.
"This report shows that according to the best available evidence, no turkey meat from areas previously infected with avian influenza in Hungary was received at the Bernard Matthews plant in Holton," said FSA chief scientist Andrew Wadge.
"It is important to remember that this investigation has always been about the illegality or otherwise of meat imported into the UK , and not about food safety. We reiterate our advice that properly cooked poultry meat does not pose a food safety risk".
Shadow minister for agriculture Jim Paice said: "The most plausible route of transmission is associated with the importation of poultry products via Hungary, yet apparently no laws have been broken. This clearly raises important questions about the precautionary measures taken by the EU, especially the issue of in-country movements prior to export.
"This report must not be the end of the matter - further studies into the control of avian influenza are urgently required."