The NIA suspects three low-intensity blasts in Haryana this year were the handiwork of a single person conducted as part of a 'dry run' ahead of a possible terror attack.
The anti-terror probe agency has submitted its report to the Haryana police on the blast that took place inside a bus near Pipli on May 26 which bore "striking similarity" to the explosions that occurred on January 16 and May 13.
The explosion on a passenger bus near Pipli had left eight people injured. The vehicle was on way from Sonepat in Haryana to Chandigarh.
Earlier, on January 16, a bomb blast had taken place on a passenger train at Panipat railway station. The explosive material was planted in a compartment next to the engine, but there were no casualties.
On May 13, an explosion had rocked an EMU train which had reached Panipat from Delhi and had been moved to the yard. There were no casualties.
The NIA has said in its report that Ammonium Nitrate and Potassium Chlorate had been used in all the three explosive devices which were attached to a clock with a 12 volt battery as a triggering mechanism.
The bomber, it said, seemed to be improvising on the explosive devices as in the January blast a cardboard box was used to pack the material which was followed by a plastic box in the May 13 incident and now an aluminium box, the sources said.
Normal adhesive tapes were used in packing the explosive material in the first two bombs but in the latest blast the bomber had used surgical tapes whose adhesive qualities are much better, the sources said, adding the reason why no large-scale damage was done was that no shrapnels had been used.
The serial number of battery used in the Pipli was not destroyed in the blast and it could help the investigators crack the case, they said.
