On the day the serial blasts occurred in Hyderabad, the city police had announced its biggest catch in counterfeit currency — Rs 2.36 crore from four persons allegedly associated with the ISI and Dawood Ibrahim. Hyderabad police commissioner Balwinder Singh said today that his investigators were probing all angles. “The angle of a link between the blasts and the fake currency is also being examined,” he said.

Meanwhile, what has got investigators interested is the timer and trigger mechanism used in the Varanasi and Hyderabad blasts.

Initial investigations, sources said, shows that the same type of quartz watch timer was used. An alarm is set in the watch and when it rings, the circuit is completed leading to an explosion. These are small alarm clocks with 9 volt batteries connected to a detonator.

In both cases, the perpetrators have relied on locally available material to make a simple but effective circuit and have used a set of two detonators. This, sources said, is done to ensure a back-up in case one of the detonators were to fail.

In Varanasi, pressure cookers were used to store the explosives while in this case there were wooden cartons filled with ball bearings that have caused maximum injury.

Clearly, this strengthens the assessment that this is the handiwork of the Harkat-ul-Jehadi Islami (Bangladesh) with the help of some Pak-based groups and local contacts. HUJI was also behind the Varanasi blasts and it figures in the chargesheet.