The H5 bird flu virus has been found on a turkey farm in south-eastern France, France's agriculture minister said this morning.
But Mr Dominique Bussereau said more tests were needed to determine if the case involved the H5N1 strain.
If confirmed, it would be the first time the disease had spread to poultry stocks in France - the EU's largest poultry producer.
Yesterday, authorities sealed off a farm with more than 11,000 turkeys in the south-eastern Ain region, the same area where France's first two cases of the deadly virus - in two wild ducks - were confirmed.
"The suspicion that we had yesterday, which brought us to first cull the animals and then destroy them, was unfortunately confirmed this morning," Mr Bussereau told France-2 television.