Taiwan has discovered two strains of avian flu in migratory birds in the northern part of the island, the first cases to be found since the start of 2004, the government said on Wednesday.

No cases of the deadly H5N1 virus, which has killed at least 12 people in Thailand this year and 20 in Vietnam, have been found so far in Taiwan.

However the agriculture ministry said on Wednesday that during routine testing it had found one migratory bird infected with the milder H5N2 strain of the virus and another bird with the H5N6 strain.

The island slaughtered over 400,000 fowl early in the year after discovering birds infected around the island with H5N2, which cannot be transmitted to humans.

The ministry gave no details on the H5N6 strain.

The ministry is conducting tests on surrounding areas, but has not announced any plans for more culling of birds.

The number of birds that have been slaughtered in Taiwan is still only a tiny fraction of the 377 million chickens the island bred in 2002, in addition to 31 million other edible fowl, such as ducks, geese and turkeys, according to the government.

Animal health officials said the source of the virus is a mystery, but suspect migratory birds or fowl smuggled from China.