Seven more students in the Indian city of Jalandhar have tested positive for swine flu, raising the total number of those infected in the country to 30.
The students belong to a group who returned from a trip to the US recently. One of them had already tested positive over the weekend.
The government has urged Indians to defer plans to travel abroad until the disease is under control.
Last week the World Health Organization (WHO) declared a global flu pandemic.
The swine flu (H1N1) virus first emerged in Mexico in April and has since spread to 74 countries.
Official reports say there have been nearly 30,000 cases globally and 141 deaths, with figures rising daily.
Doctors in Jalandhar city said the affected students are between 14 and 17 years of age.
They were part of a group of 31 students and three teachers who returned over the weekend after a 10-day educational trip to the US.
Indian officials say they have tracked down eight people who were sitting near the group of students on the flight to Delhi from New York.
"They have been advised to watch for flu symptoms and take adequate precautions against possibly spreading the virus," an official said.
Separately, federal health minister Ghulam Nabi Azad has urged Indians, especially students, to put off travelling abroad till the flu was under control.
"Till the disease is controlled globally, I would like to request young people from educational institutions going abroad that they can suspend their visits from the time being," he was quoted as saying by the Press Trust of India news agency.
Fresh cases have been detected in the northern city of Jalandhar, as well as Hyderabad and Bangalore in the south.
Earlier this month, India issued an alert against the flu. Airport screening has been tightened and more testing facilities would come.
The government has said that India was fully equipped to deal with the outbreak.