Another person - Hasan Saheb - who was also injured in the blast later gave some information to the sleuths of central intelligence agencies that led to arrest of two women including wife of one of the dead men and six people from Assam, the sources said.
However, after initial help in the arrests, neither the state police nor the NIA could make any headway in the case with instances of alleged failure in nabbing some of the accused, the sources said.
The NIA, which was being assisted by the state police was unable to prepare sketches of either Sajid and another suspected Bangladeshi national Nasirullah who is also believed to have managed to escape the clutches of investigators.
Only two people arrested from Assam could give some information about the incident which included claims that Improvised Explosive Devices (IEDs) could have been smuggled into the neighbouring Bangladesh. However, the two could not provide any information about how explosives were transported.