NEW DELHI (Reuters) - Only a month after authoritiesdeclared bird flu was under control in eastern India,veterinary workers began culling thousands of chickens onMonday to contain a fresh outbreak in poultry.

The outbreak was reported from West Bengal's Murshidabaddistrict where 900 chickens and ducks died over the last twoweeks, officials said.

In January, the H5N1 virus had hit 13 of the state's 19districts, including Murshidabad, bringing down poultry salesby more than 70 percent in the state, but it had a limitedimpact in rest of the country.

Authorities in West Bengal then culled more than 3.4million birds in the state after the World Health Organization(WHO) described January's outbreak as the worst-ever in India.

There have been no reported human cases of the bird flu.Experts fear the H5N1 strain could one day mutate into a formeasily transmitted from person to person, leading to a pandemicthat could kill millions worldwide.

Officials in eastern India say bird flu among poultry couldspread to new areas.

"We do not know how many chickens and ducks escaped cullingduring the earlier exercise, but we are now trying our best tofind them," Anisur Rahaman, the state's animal resourcesminister told Reuters from the state capital, Kolkata.

Bird deaths were also reported from neighboring Birbhumdistrict, the epicenter of the original outbreak in January.

"We don't think it is bird flu, but we are collectingsamples from Birbhum for testing," Rahaman said.

SMUGGLED POULTRY

The minister said smuggled poultry from bird-flu hitBangladesh could have triggered the latest outbreak.

Bird flu spread to another district in Bangladesh lastweek, affecting 47 out of 64 districts in the country,struggling to contain the outbreak.

In India's bordering district of Murshidabad, over 350veterinary workers were catching chickens and ducks on Mondayfrom homes and slaughtering them by wringing their necks,officials and witnesses said.

Trade associations in New Delhi said the latest outbreakcould impact on the demand for maize and oilmeal from thepoultry industry.

"The demand of maize may go down. Possibly the prices maysoften to an extent," said Amol Sheth, president of the AllIndia Starch Manufacturers Association.

At least 50,000 chickens and ducks will be slaughtered inthe next few days to contain the latest outbreak, a seniordistrict official said.

Earlier culling efforts had been hampered when villagersrefused to hand over their chickens and even let them loose toavoid getting caught.

"We are determined to cull all backyard poultry in a 5 km(3 miles) radius and ensure a better job this time," SubirBhadra, a senior official said.

While India has so far not reported any human infection,but health workers were moving in villages to look for peoplewith flu-like symptoms.

"We are well-prepared and a strict surveillance is in placenow," Rahaman said.

The WHO said recently the virus was firmly entrenched inAsia and a pandemic among humans was possible.

(Additional reporting by Biman Mukherji; Editing byAlistair Scrutton and David Fox)