India put 26 people in isolation after they fell sick while culling poultry in a state affected by bird flu, while medical staff were monitoring hundreds of others, officials said on Friday.
Those quarantined in West Bengal complained of fever and respiratory distress over the past few days, but health staff said it was unlikely they had bird flu.
India has not reported any human infection of the H5N1 bird flu virus in its four outbreaks of avian influenza since 2006.
"The preliminary tests for bird flu are negative, but more tests are being conducted and the list of sick people reviewed every day," RS Shukla, a senior health official, told Reuters.
Bird flu has spread to 13 of West Bengal's 19 districts, spelling trouble for parts of India's poultry business.
Egg exports from the world's second largest producer have dropped about 50 per cent in the past two weeks, leaving the industry with losses of around $20 million, trade officials said.
Consumption of poultry products has fallen to negligible levels in West Bengal, but chicken sales are recovering in the rest of India after an initial wobble when the latest outbreak was announced.
Veterinary staff have culled 2.6 million birds, completing what officials said was a successful operation that had brought the bird flu situation under control.
"We are aware of the consequences of a possible human infection and we are taking all possible measures," Surjya Kanta Mishra, the state's health minister said.
Bird deaths were reported from Haryana, close to New Delhi, but authorities said preliminary tests for bird flu had turned up negative.
"There have been some deaths, but these are due to septicaemia and not avian flu," VP Nehra, a senior animal husbandry official said.