GUWAHATI, India, April 22 (Reuters) - Authorities in a remote northeastern state of India prepared to cull thousands of chickens after a fresh outbreak of bird flu in poultry was detected on Tuesday, officials said.

More than 25,000 chickens and ducks have already been slaughtered in Tripura state this month after eight villages were hit by the H5N1 strain.

On Tuesday, officials said bird flu had spread to a new area.

"Bird flu has been confirmed for the second time in Tripura," Kartick Debbarma, a senior animal resources official said in Agartala, Tripura's capital. "It is the H5N1 strain."

The remote northeastern state borders Bangladesh, where more than half the country's districts have been affected by the virus.

In India, the virus resurfaced in the eastern state of West Bengal in January this year, forcing authorities to cull more than four million birds.

Since then the virus has flared up intermittently, hitting poultry sales in the region.

Many states banned poultry products, pulling down prices sharply and prompting farmers to cut production.

The World Health Organization described the January outbreak in West Bengal as the worst ever in India.

Officials in Tripura said they were holding meetings and drawing up their strategy to contain the disease, which has hit Mohanpur, a town just 20 km (12 miles) west of Agartala.

Health department officials were also checking humans for any flu-like symptoms.

While no human cases have been reported in India, experts fear the H5N1 virus might mutate or combine with the highly contagious seasonal influenza virus and spark a pandemic that could kill millions of people.

Since the virus resurfaced in Asia in late 2003, at least 240 people have died from bird flu in a dozen countries, the WHO says. (Reporting by Biswajyoti Das; Editing by Bappa Majumdar and David Fogarty)

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