The US had around 11 million illegal immigrants in January 2010 and India was a major "source country" for them, according to an official report.
The document released by the Department of Homeland Security's Office of Immigration Statistics, said Mexicans continue to make up 62% of the total number.
However, the number of unauthorised immigrants has dropped by one million from the record 11.8 million in the country in January 2007. Between 2000-2010, the number of those living in the US illegally grew by 27%.
Of all the undocumented immigrants in the US, 39% entered in the year 2000 or later.
Most unauthorised immigrants "either entered the US without inspection or were admitted temporarily and stayed past the date they were required to leave", the report said.
Between 2000-2007, the unauthorised immigrant population had grown by 3.3 million, from 8.5 million to 11.8 million, signifying an average annual increase of 500,000 people.
The number of unauthorized immigrants dropped to 11.6 million in 2008, and to 10.8 million in 2009 during the economic crisis in this country.
By regions, the report said some 8.6 million unauthorised immigrants - 80% - come from North America, Canada, Mexico, the Caribbean and Central America.
In second place comes Asia with one million, followed by South America with 800,000.
Between 2000-2010, the biggest increase took place among natives of North America (2.5 million) and the greatest decline was among natives of Asian countries (200,000).
Mexico continued to be the chief source country of unauthorised immigrants. There are 6.6 million unauthorised immigrants from Mexico in the US, which represents 62% of the total.
Last year the leading source countries of unauthorised immigrants were El Salvador (620,000), Guatemala (520,000), Honduras (330,000), and the Philippines (280,000).
India, Ecuador, Brazil, South Korea and China, in that order, complete the list of the 10 countries that together make up 86% of the undocumented population.