"We do not rule out the possibility of humans being affected, and it is a distinct possibility," Press Trust of India news agency quoted P.K. Hota, India's health secretary, as saying on Wednesday.
However, he told reporters that if the tests were positive, those infected would have only a "mild episode".
As health workers killed thousands of birds in India, authorities said that the first laboratory reports on whether the bird flu virus had infected people were likely to be delayed.
The results from 12 people, including six children - quarantined either with flu-like symptom or as a precaution - had been expected late on Wednesday, but officials now say they can take up to another day.
"We do not rule out the possibility of humans being affected, and it is a distinct possibility"
India's health secretary
"Usually, this kind of test takes 72 hours. But we don't want to leave any room for doubt and hence we will follow some rigorous testing that might take a little more time," said Vijay Satbir Singh, Maharashtra state's top health official.
Chicken sales drop
NDTV television said, quoting government sources, that two of the 12 quarantined had tested positive for "mild bird flu".
But A.C. Mishra, director of the government's National Institute of Virology, denied that the tests were complete.
"We will inform the federal health ministry once the reports are ready," Mishra told Reuters. The institute is testing the throat swabs and blood samples of those in quarantine.
The health ministry said in a statement:
"As on today's (Wednesday) date, there is no human case of avian influenza. The situation is being closely monitored and under control." None of those in quarantine shows signs of pneumonia, a key indicator of bird fly infection.
Amid fears and mixed messages from the government, chicken sales dropped across the country. The army, state-owned Indian Airlines and Indian railways took chicken - an Indian staple - and eggs off their menus. Parliament, too, has stopped serving chicken in its cafeteria, media reports said.
Amid fears of a pandemic, chicken
sales dropped across India (File)
However, other government officials tried hard to reassure people that properly cooked chicken and eggs were safe. Top health officials ate chicken at a news conference in New Delhi.
India pressed ahead on Wednesday with its massive slaughter of chickens to halt the spread of the H5N1 bird flu virus.
Reports of thousands of poultry deaths poured in from across the country, the latest from the southern state of Karnataka, where 16,000 dead chickens were found.
More than 700,000 birds have been killed in the Navapur district of Maharashtra, in western India, since tests of 30,000 chickens that died in recent weeks detected the virus.
Dead poultry have also been reported in Gujarat, northern Uttar Pradesh and West Bengal states.
Bird flu has killed more than 90 people in seven countries since 2003. While the virus is hard for people to catch, experts fear it could mutate to spread person-to-person, sparking a pandemic that could bring economic chaos and overwhelm health services.
Ban on drugs
Meanwhile, a federal health official, who asked not to be identified because of the sensitivity of the matter, said the government was considering a ban on retail sales of a generic bird flu drug, fearing the disease could develop resistance if taken by people who are not infected by the H5N1 strain.
India is considering a ban on retail
sales of a generic bird flu drug
Two Indian pharmaceutical companies are making generic copies of Tamiflu, a patented drug from Swiss drug maker Roche that is believed to be effective in treating symptoms of bird flu in humans.
One of the companies, Cipla Ltd., said on Wednesday that it had started shipping the drug to pharmacies. Cipla's generic copy costs 1000 rupees ($22) per pack of 10, a third of what Tamiflu costs.
The other company, Hetero Drugs Ltd., said it was only supplying the drug to the government, and has delivered 700,000 capsules.