The purported admissions of Lt. Col Prasad Purohit may have suddenly expanded the scope of the Malegaon probe with even the Rajasthan police now sending a team to examine links with the Ajmer Sharif blasts but as it turns out, the entire effort boils down to a reality that hit investigators over a year ago.

Towards the end of 2007, sources said, it was clear — based on forensic and scientific evidence available until then — that India was being hit by two kinds of bombs that were distinguished not so much by the chemical used as explosive but more by the “character” of the bomb itself, its circuits and elements.

The first were the C-shaped open wooden boxes that held the circuit through holes on the side for wires to pass. The explosive was essentially tightly packed ammonium nitrate, held together by fuel oil or nitrogen gel, metal balls and nuts for splinters and had an alarm clock for a timer (the famous Prince or Samay watches). These were the ones which went off in UP, Ahmedabad, Bangalore, Delhi, and, possibly, even Jaipur.

The second type of bombs were mostly found in metal pipes with grooves in single rows on one side and spiraled on the other. These pipes were filled with explosives, not always the same type and this is what initially confued the investigators. But they were usually in tin boxes or a suitcase. Strikingly similar here were bombs found in the Samjhauta Express last February, Mecca Masjid blasts last May, and Ajmer Sharif blasts last October. So investigators concluded that there were two groups with two distinct styles of bomb-making at work.

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