AGARTALA, India, April 6 (Reuters) - A fresh outbreak of bird flu has been reported in poultry in one of India's remote northeastern states, a top veterinary official said on Sunday.

Veterinary workers were preparing to slaughter thousands of chickens and ducks in Tripura state, bordering Bangladesh, after preliminary reports that more than 3,000 birds had died, officials said.

"It is bird flu and the final report is expected tomorrow," Ashis Roy Burman, director of Tripura's Animal Resources Development Department told Reuters in Agartala, state capital.

"The virus must have spread from Bangladesh." Authorities in Bangladesh have culled millions of birds but are still struggling to contain the virus.

In India's eastern state of West Bengal, authorities said the deadly virus had resurfaced in Nadia district, which also borders Bangladesh.

West Bengal had briefly contained the outbreak by culling nearly four million birds in 14 of its 19 districts, but the virus has intermittently resurfaced.

"We will again have to cull more birds," Anisur Rahaman, West Bengal's animal resources minister said by telephone from state capital Kolkata.

Health workers in both states said they were looking for people with flu-like symptoms.

India has not reported any human infections so far, but experts fear the H5N1 strain could mutate into a form easily transmitted from person to person, leading to a pandemic.

Since January, poultry sales in West Bengal have fallen by about 70 percent and traders are struggling.

India reported it first outbreak in 2006 in the western state of Maharashtra.

The World Health Organization described the January outbreak in West Bengal as the worst ever in India. (Writing by Biswajyoti Das; editing by Bappa Majumdar and Andrew Roche)

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