French vets have said they cannot rule out Avian Influenza (AI) after 4,000 chickens died on a French farm on Saturday 16 December.
Tests are being carried out to determine the cause of death, which the farmer said was totally unexpected. His flock of 7,000 had appeared healthy on Saturday morning, but by evening 4,000 were dead on the farm in Sarrey in the Haute-Marne region.
"In the absence of another explanation, we cannot rule out the theory of avian flu," said an official of the French Veterinary Services Directorate on France-Info radio.
"We are obliged to speak of suspicion."
The farm has been sealed off by French authorities until tests are completed.