Police officials inspect IEDs kept in buckets. A Telegraph picture

Siliguri, April 3: The three victims of the blast in Champasari today are believed to have been active members of a militant group who were clandestinely putting together improvised explosive devices (IEDs) and planning a strike which police and intelligence agencies are yet to lock on to.

The manner in which the three youths and the woman stayed in the tin-roofed house, keeping to themselves and not mixing with either their neighbours or their landlord was typical of such behaviour, police sources said.

The discovery of timer devices and two plastic jars with the live IEDs points to the intentions of the group. “There is absolutely no doubt that these men and the woman were linked with an insurgent outfit,” an investigating official said.

Criminal Investigation Department (CID) officials, who visited the spot, said the blasts occurred because of the mishandling of the IEDs. “Primary investigation indicates the quartet might have been from Nepal,” the officer said.

D. Sengupta, the director of the Central Forensic Science Laboratory, told The Telegraph over phone from Calcutta that RDX or ammonium nitrate usually creates a crater at the blast site. “After the blast, a shock wave is created in the area, which blows away substances close to it.”

When told that all the three deceased had lacerated wounds and severe burns, the veteran forensic expert said it might have been caused because of the explosives that had split during the blast.

“A fireball can form after the blast and burn anything that came its way. There are chances that such a fire might have led to burn injuries,” he added.

Minister Asok Bhattacharya said his fears have come true. “Intelligence officials had precise information that some seditious forces were attempting to spread unrest in Siliguri. I had said this earlier and today, my apprehensions came true,” he said over phone from Coimbatore.

The inspector general of police (north Bengal), R.J.S. Nalwa, however, said nothing could be said till the investigation was completed.

“We need to check out whether they were making IEDs ever since they were staying there,” Nalwa said.