More than 50 birds have died at a UK quarantine center hit by an outbreak of avian flu.
A new report says a consignment of Taiwanese mesia birds was the most likely source of the outbreak.
An investigation was launched last month after samples from dead birds from the Essex facility tested positive for the H5N1 strain.
Some 53 of the 101 Taiwanese birds died, though the report was unable to say how many were killed by the flu.
The report said "on the balance of probabilities" the infection was introduced to the facility by a consignment of mesias, but did not appear to have been passed on to other species held there.
Chief Veterinary Officer Debby Reynolds said: "This report contains significant epidemiological findings and helps to further our understanding of highly pathogenic avian influenza.
"In particular the apparent lack of transmission of H5N1 between species in the facility will be of interest to the international community."
In a written Parliamentary statement, Environment Secretary Margaret Beckett said: "This report will be fed into the independent review of avian quarantine procedures I announced on October 31 led by Professor Nigel Dimmock and to Essex County Council who are conducting an investigation into events at the quarantine facility."
The virus detected is most closely associated with Chinese ducks.