Tamil Nadu CB-CID police is working on some leads which they have stumbled upon in connection with the twin bomb blasts on the Bangalore-Guwahati Express today that left one woman dead and 14 others injured.
Sources in the investigation agency said they were also looking into whether the suspected ISI agent, a Sri Lankan national Mohammed Zahir Hussain, arrested two days ago, had any role into the blast.
However, top officials of the CB-CID wing remained tight-lipped over the investigation.
A police official involved in the investigation told on condition of anonymity that they suspect that the blast would not have been possible without the involvement of "home-grown terror modules".
Meanwhile, preliminary probe into the nature of bomb suggest use of chemical compounds like ammonium nitrate along with a "known combination of some combustible elements", sources said.
Sources in the intelligence wing rejected reports that there were specific inputs about the blast to the state from the Centre and asserted that the inputs that were shared by the Centre was of "routine" nature like the need for enhanced vigil during elections.
Meanwhile, police said two persons who had been detained for questioning have been let off as there was no evidence to prove their role in the blast.
An FIR has been filed by the Government Railway Police against unknown persons. Several sections of the IPC, Explosives and Railway Acts have been invoked based on a formal complaint from the Chennai Central Deputy Station Manager Balasubramanian.