Bird flu has been found at a second farm in Redgrave, Suffolk.
It comes weeks after a highly pathogenic strain of the virus was discovered at Bridge Farm in Redgrave.
The virus was found on the premises but not in the birds at Gressingham Foods.
Defra say it is not a separate outbreak. Investigators detected presence of the virus at a separate farm while carrying out routine tests.
55,000 ducks will be need to be culled to contain the spread of the virus.
Public Health England says that the risk to public health from the virus is very low and the Food Standards Agency says that bird flu does not pose a food safety risk for UK consumers.