"Now we can say it is definitely bird flu," Pradip Kumar, a ministry official, said adding that 250,000 birds would be culled
Kumar said bird flu cases had been reported in two administrative districts in the state of West Bengal. He said the outbreak was reported at private farms in the Birbhum District, some 250 km (160 miles) from the state's capital, Calcutta, and at a state poultry farm in a nearby district.
The affected area has since been cordoned off and is under surveillance, the official said.
In 2006, India reported a bird flu outbreak in the state of Manipur, in the northeast of the country. Hundreds of thousands of chickens were slaughtered at the time.
Although no cases of human-to-human transmission of avian influenza have been reported, scientists fear the virus could mutate into a strain that could pass easily from person to person, causing a global pandemic.
More than 200 people have died worldwide from bird flu since the first fatality was registered in 2003, according to the World Health Organization.
