NIA investigations into the case found that Karim was a resident of Kafirpur Kirnahar in Birbhum and all necessary tests were conducted before announcing the identity of the second person.
Karim, along with Sakil Ahmed, owner of the blast-hit house in Burdwan's Khagragath, was killed when the explosive material accidentally went off. Karim died on his way to the hospital.
It is suspected both had links with banned terror group Jamaat-ul-Mujahideen Bangladesh (JMB).
The identity of the second person was established after NIA made a headway in its probe and arrested two--Sajid and Amjad Sheikh--of the 12 main accused wanted in the case.
Another person Hasan Saheb, who was also injured in the blast, gave some information which led to the arrest of six people in Assam. However, only two women including the wife of one of the dead man, gave some sketchy information about the blast conspiracy.