A World Health Organization official says the North Korean bird flu was apparently propagated via migratory birds.

WHO acting director in Pyongyang Tej Bir Walia told Radio Free Asia Tuesday said that local chicken farms where the disease broke out often experienced power blackouts.

He conjectured that migratory birds had entered the plants through windows opened during power stoppages, infecting poultry with the avian influenza.

In February, the North announced that it had culled over 200-thousand chickens after a bird flu outbreak out at three major poultry farms, including one close to Pyongyang.