Starting from the kind of explosives used in Sunday’s blast on the Samjhauta Express, investigators have put a whole set of such attacks under the scanner, from Malegaon six months ago to even one in Punjab in 2002 trying to work on clues emerging from the similarity in method.

What’s important in all these cases is that low-intensity explosives were used. It is quite similar to what was found in Panipat — small amounts of potassium nitrate with sulphur, along with carbon and magnesium wires. All this was packed with either kerosene or petrol bottles lined up alongside in the suitcase. And covering all this were some clothes. Orpat digital watches were used as timers, just as in Malegaon. The explosion was small but enough to ignite a huge fire.

Sources say this underlines the recent trend among terrorists to use locally available material for making explosives but enough to cause widespread damage. Even in Malegaon, RDX was used in small quantities as the “core-explosive” with an aim to maximize the impact of the blast. The purpose: to throw off investigators by erasing the “signature.”

Given that this is the first major case where Pakistan nationals have been targeted on Indian soil, investigators are cautious about attributing the motive to Pakistan-based terror groups. At the same time, they are not ruling out the possibility of involvement of locals “handled” by individuals in Pakistan. Working on a few leads, including the two who are said to have got off from the train before Diwana, security agencies are working hard to ensure that this, too, doesn’t enter the list of inconlusive investigations into terror blasts.

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