German officials have culled about 160,000 ducks as a precaution Sunday after the deadly H5N1 bird-flu virus was found in a poultry farm near the southern city of Erlangen. A federal lab confirmed nearly 400 birds were found dead of the "highly pathogenic" H5N1 variant.

The officials called it as the biggest ever culling operation in Germany as on date. Officials are not sure where the infected animals came from but it is speculated that they belonged to another poultry farm in the northern state of Lower Saxony.

Bavarian Health Secretary Otmar Bernhard told DW-World, "We have not been able to pinpoint the source of outbreak." The officials have sealed off the area around the farm.

The H5N1 strain of avian influenza is fatal to humans but cannot yet be transferred between humans. It has hit wild water-birds and some domestic goose in other parts of Germany in July.

The H5N1 virus has killed more than 190 people worldwide, according to the World Health Organization. Experts fear that bird flu could mutate into a strain that could be transmitted among humans, potentially leading to a global pandemic.