Panna Ismail and Bilal Malik, arrested in a joint operation by Tamil Nadu and Andhra Pradesh police at border town of Puttur on October 5, and 'Police' Fakruddin, nabbed a day earlier, have been named in the chargesheet filed before the First Additional Chief Metropolitan Magistrate's Court.
The chargesheet was filed after examining 260 witnesses and is in three volumes with 7,445 pages of material and 201 documents, police said.
The blast in front of the BJP's Malleshwaram office on April 17, ahead of the May 8 Assembly polls, had left 18 persons injured and damaged 23 vehicles and 56 buildings.
Malik, Ismail and Fakruddin are key suspects in various cases, including an attempt to kill BJP veteran leader L K Advani by placing a pipe bomb on his yatra route near Madurai and the murder of other Sangh Parivar leaders in Tamil Nadu.