Quoting a report of West Bengal Intelligence, BSF DG A Mitra said these Bangladeshis had mostly entered via the West Bengal border between 1972 and 2005 and it was not easy to identify them.

Admitting that influx from Bangladesh and Pakistan was a continuing menace, Mitra said the BSF had apprehended 3,381 infiltrators this year so far. "Infiltration is a phenomenon that has been going on since years. It has not started recently," he said.

Mitra said the Karimganj and Dhubri sectors of the North East are particularly vulnerable to infiltration.

When told that the proposed floating border outpost on the Brahmaputra in Dhubri has been a non-starter, IG (Assam-Meghalaya frontier) PK Mishra said each outpost in the riverine area of Dhubri has four speedboats. "It is much easier to conduct patrolling in speedboats than go for surveillance on floating border outposts."

Mishra said the perennial floods in the Brahmaputra are also a reason that has prompted the BSF not to set up floating border outposts in the region.