Antibody tests showed Tuesday that chickens at seven more farms in Ibaraki Prefecture may have been infected with a bird flu virus of the H5 strain in the past, the prefectural government said.
Chickens at two farms near the seven in the town of Ogawa have already tested positive for antibodies to the virus.
The prefectural government imposed a ban on transferring chickens and eggs from an area surrounding the seven farms to places outside.
It will also decide whether to cull the chickens at the farms after hearing from an expert panel of the Ministry of Agriculture, Forestry and Fisheries.
The prefectural government has confirmed that chickens at 14 farms were infected with the avian influenza.
The story comes from Kyodo News.