According to Basab Talukdar, chief immigration officer, eastern India: "The number of illegal immigration cases is on the rise. It is a cause of concern as these immigrants are constantly devising new ways to deceive airport officials."

He added that the airport's immigration department had procured new equipment in April this year to keep a check on illegal immigration.

Airport officials also admitted that people from the western and northern parts of India have been using the NSCBI airport to travel illegally out of India. "People often tend to use languages that act as a barrier for our officials. They are not conversant with Marathi, Gujarati or Punjabi," said an immigration officer.

He added that most of these people are headed for the USA and Europe looking for jobs. In 2002, 30 cases were registered. The number went up to 53 in 2005.

"Forgery of passports is on the rise, necessitating the deployment of advanced gadgets," said Police Commissioner Gautam Mohan Chakrabarti.

Till May 2008, twelve cases had been registered with the immigration department that included tampering of passports, forging of visas, forging of arrival and departure stamps and even human trafficking.

The immigration department has also been maintaining a record of touts and travel agents who help the illegal immigrants in forging visas or tamper with passports. These touts are mainly based in Bangkok, Gorakpur, Kolkata airport and Vadapalani in Chennai.