Bird flu has just been spotted in Vietnam's northern Son La province, where poultry has not yet been vaccinated against the disease, according to sources from Vietnam Veterinary Department Wednesday.

Thirty-one chickens in two flocks in Moc Chau district died recently after showing bird flu symptoms, and 25 ducks in Mai Son district were also suspected to die of the disease. The local veterinary authorities have culled 95 ducks.

The deaths' causes have not yet been confirmed. The province is waiting for final testing results.

According to reports from several bird flu-hit localities, some fowls, which have been vaccinated, still died en masse. One of the causes may be the vaccines' poor quality, or the vaccines used were not the right type regulated by local agencies.

Since early last month, bird flu has been spotted in 85 communes of the 14 northern, central and southern localities, namely Bac Lieu, Dong Thap, Hanoi, Bac Giang, Quang Nam, Thanh Hoa,Hai Duong, Hung Yen, Ninh Binh, Hai Phong, Quang Ngai, Vinh Phuc, Bac Ninh and Son La, killing and leading to the forced culling of over 436,000 fowls.

Previous outbreaks starting in December 2003 killed and led to the forced culling of some 46.6 million fowls in Vietnam, causing losses of 3.5 trillion Vietnamese dong (221.5 million US dollars).