Stating that the bombs were “made and planted with great precision”, Dr Kaushal added: “Studying the spread of fire and other clues in the two coaches, it is clear that the fire spread towards the centre. Clearly, the motive was to explode the bombs at either end to jam the doors, so that there was no escape route left.” While all four doors of one coach could not open, only one door of the other coach could be opened.

Forensic officials said the bombs went off at the set time after sparking in the electronic “light-emitting diodes” that were part of the connecting circuit. The sparking led to an explosion in the pipes containing potassium nitrate with sulphur, along with carbon and magnesium wires. This then spread to the kerosene-petrol bottles.