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GUWAHATI, India, Nov 28 (Reuters) - Authorities in India's northeastern state of Assam have ordered culling thousands of chicken and ducks after a fresh outbreak of bird flu in poultry was detected late on Thursday, a senior official said.

"We were informed that the samples sent to laboratories in Bhopal and Pune have been tested positive. So we have ordered for culling in the area, which will start today," R. C. Jain, a senior state government official said on Friday.

"It is H5N1 stain," he said in Guwahati, the region's biggest city.

More than 30,000 chickens and ducks would be slaughtered in next three days in 20 villages, after one of them was hit by bird flu, officials said.

Authorities started to worry about a new outbreak after hundreds of poultry died in Rajabazar village, just 35 km (21 miles) west of Guwahati.

India has not reported any human infections so far, though the first outbreak in poultry was reported in 2006 in the western state of Maharashtra.

Experts fear the H5N1 strain could mutate into a form easily transmitted from person to person, leading to a pandemic. (Reporting by Biswajyoti Das; Editing by Alistair Scrutton)

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