Indonesia has investigated the cause of creation of the new strain of bird flu virus following the death of hundreds of thousands of ducks since November, agriculture minister said Friday.

The investigation was made following the finding of a highly pathogenic avian influenza sub-type H5N1 with clade 2.3, which is different from the clade previously found.

Indonesian Agriculture Minister Suswono Arsyaf said that his ministry has set up a task force to find out the cause of the new clade.

"We are tracking down the main cause (of the creation of the new strain), there are some possibilities on it," Suswono said.

Pujiatmoko, dirfector of animal health of the ministry, said that another possibility was that the new strain has already existed in Indonesia but it had not been detected in the past.

Over 320,000 ducks have died in several provinces in Java island since November, Ade Meirizal Zulkarnaen, chairman of the national poultry breeder association, told Xinhua by phone.

Indonesia has culled millions of poultry since the bird flu hit the vast archipelago country in 2003. The virus also killed 159 people in the country out of 359 fatalities worldwide, according to the WHO.