KOLKATA, India, May 8 (Reuters) - Indian authorities were testing dead poultry for bird flu in an eastern state after more than 3,000 birds were found dead, officials said on Tuesday.

The dead chickens were found over the past two days at poultry farms in remote Matigara village in West Bengal, close to the border with Bangladesh that has witnessed several outbreaks of the H5N1 bird flu virus in fowl this year.

An official in the Indian capital said post-mortems of the birds done by investigators revealed the most likely cause of death was Newcastle disease along with infectious bursal disease.

"But some samples have been sent to Bhopal for further tests for avian influenza as a matter of precaution," said Upma Chawdhry, joint secretary of the federal Department of Animal Husbandry, referring to a state laboratory in the city of Bhopal.

Matigara village in West Bengal"e;s Darjeeling district is 25 km (16 miles) from the Bangladesh border.

Healthcare workers buried hundreds of birds in huge pits at poultry farms in the area and sprayed disinfectant over the sites.

Chawdhry said that a poultry farm with about 11,000 birds had been affected. West Bengal said it was not taking any chances.

"We have sealed the entire border with Bangladesh to stop any one trying to sneak poultry into India," Anisur Rahaman, West Bengal"e;s animal resources development minister, said in Kolkata.

West Bengal shares a 2,200 km (1,370 mile) porous frontier with Bangladesh.

New Delhi was praised by international agencies for its handling of bird flu outbreaks in western India last year, especially giving quick compensation to farmers.

Bird flu has killed more than 170 people since late 2003, according to the World Health Organisation. At least 200 million birds have died. (Additional reporting by Kamil Zaheer)