Over 100 experts from Assam will arrive in West Bengal on Monday to assist in culling operations, which have been delayed even as the H5N1 virus spread to 21 blocks of six districts in West Bengal.

State Animal Resource Development Minister Anisur Rehman said that 1.65 lakh chickens were culled till Sunday, though it fell far short of the targeted figure, which has been raised  to seven lakh from the previous target of four lakh.

Unable to give a deadline for meeting the target, the minister told PTI, "Several factors were delaying culling operations."

"Lack of awareness among the villagers, resistance from the poultry owners and dearth of veterinary staff capable of carrying out culling operations are slowing down the operations," he said.

Five hundred culling teams have been deployed in the affected districts, the minister said. The experts from Assam will be deployed in Burdwan district, he added.

The state government was mapping the extent of spread of the virus to have a better idea of the exact affected areas, he said.

All possible efforts were being undertaken to contain the spread of the virus and to check its transmission to human beings, he said.

Bird flu [Images] spread to Bankura, the sixth district in the state and to seven blocks in Murshidabad and Burdwan districts, on Sunday. Poultry deaths were also reported from new areas, including Darjeeling and Coochbehar.

Bird flu spread to the sixth district -- Bankura � on Sunday as samples sent from Saltora block tested positive. A report from Bankura said that five teams comprising 50 men fanned out to the blocks for culling operations today.

Reports of chicken deaths had come in from Dahula village in Saltora block also.

Bird flu deaths spread to three new blocks in Murshidabad district and four blocks in Burdwan district on Sunday, following which culling operations were stepped up.

A senior veterinary surgeon from Delhi and another senior officer will visit Murshidabad district to oversee the entire work in the district, official sources said in Berhampur.

In Nadia district, samples from seven villages in Chachal sub-division, from where bird deaths were being reported, were sent to Kolkata for testing. Fifteen teams comprising 75 personnel were carrying out culling operations in the district on Monday.

In South Dinajpur district, where bird flu was first reported in a state-owned poultry at Balurghat and confined to a 5 km area, the virus has spread to Gangarampur sub-division, 25 km from Balurghat.

Samples were being sent to Bhopal and door-to-door culling operations were being taken up in the district, which has exceeded the culling target of 40,000. Nearly 53,000 birds have been culled in the district till Monday.

Poultry deaths were also reported from new areas of the state including northern districts of Darjeeling and Coochbehar.

About 200 poultry deaths were reported in Jaridharna and Daribhasa villages in Dinhata sub-division of Coochbehar, reports said. A medical team visited the villages, collected the samples and sent them to Kolkata for testing.