Combat force personnel carry arms, laptops and other items recovered from the Birbhum residence of an accused in the Burdwan bomb blast case. (PTI)

Bolpur, Oct. 20: The NIA has found from a Bolpur house interconnected with three others half-a-dozen boxes with circuits that the agency suspects are used to detonate bombs.

The circuits were found on Saturday while a team of the National Investigation Agency (NIA) was searching the abandoned houses with holes that allowed passage from one building to another, sources said.

Wrapped in a plastic sheet, the boxes containing the circuits were found inside a well in a house belonging to Talehar Sheikh, one of the absconding suspects in the Burdwan blast case.

The four houses in Muluk village in Bolpur are said to have been built illegally on government land — an unlikely haven for terror suspects.

One of the houses belongs to Dalim Sheikh, who allegedly scouted for youths to be indoctrinated by the Burdwan module.

The two other houses were owned by Mithu Sheikh and Abdul Malek, all suspects in the case.

“We believe that the interconnected houses were used as a workshop to make IEDs (improvised explosive devices or home-made bombs) like the one in Khagragarh. We have found out that Abdul Hakim, who was injured in the blast, visited these houses several times. The circuits are used to detonate IEDs,” an NIA official said.

NIA sources said wires and switches found in one of the four houses suggested that the circuits were assembled there.

The investigators have learnt after interrogating Hakim that the module sourced explosives from also rackets that pilfer gelatine sticks from the stone quarries in Birbhum’s Mohammadbazar, Nalhati, Rampurhat and Muraroi. Hakim hails from Deucha village in Mohammadbazar,

“The explosives were ferried to suspected workshops in Birbhum, Murshidabad, Burdwan and Nadia for IED manufacturing,” said an investigator.

District police sources said that during four raids this year, they had recovered about 2,000 detonators and at least 50kg of gelatine sticks from Rampurhat, Nalhati, Muraroi and Mohammadbazar.

“We had arrested half a dozen people involved in smuggling gelatine sticks from the stone quarries of Birbhum. We came to know from the arrested persons that the explosives are smuggled out and sold at high rates. But we could not find out who bought the gelatine sticks and for what purpose,” said a senior police officer.

“We are investigating how much of the smuggled explosives found their way to terror modules. Initially, we had Maoists in mind but now we have to examine other possibilities,” the police officer added.

Around 500 stone quarries operate in Burdwan’s Mohammadbazar, Rampurhat, Nalhati and Muraroi.

Police officers accompanying the NIA team said: “No gelatine stick or other explosives were found from the interconnected houses in Muluk.”

At Dalim’s house, the NIA team found about 85 small steel containers that resembled pitchers. “Dalim was an utensil hawker. So, it was easy for him to carry the steel containers packed with explosives to different destinations,” an official said.