Jorhat, May 18: Tinsukia police have hired the services of Calcutta-based sketch artist Debashish Banerjee to proceed with the investigations in the twin blast case in the district last month.

Apart from working in several high-profile cases across India, Banerjee had earlier assisted Assam police in the investigation of Guwahati serial blasts case in 2008 and murder of agriculture department superintendent engineer Gadapani Pathak in lower Assam in 2012.

Suspected Ulfa (Independent) militants lobbed a grenade at Devipukhuri market in Tinsukia town on April 28, injuring 15 people. Earlier that morning, a bomb had exploded in front of a tea garden owner's bungalow at Guijan, on the outskirts of the town, but no one was injured. The police suspect Ulfa (I) cadres were behind the explosion.

Police believed that the blasts were an act of "retaliation" by the outfit following the killing of a militant, Rangman Gogoi alias Mekuri, at Talpathar village in Bordumsa in a joint police-army operation bordering Arunachal Pradesh on April 27.

Tinsukia superintendent of police Mugdha Jyoti Mahanta told The Telegraph today over phone that the district police had approached Banerjee sometime back to come over to Tinsukia and extend his assistance to the probe. Banerjee came to Tinsukia on Monday and has started work.

"He (Banerjee) is a well known artist and has a lot of experience in this field. He has worked in several big incidents of blasts across the country. So, we thought of hiring his services to carry forward the investigation in both the cases," Mahanta said.

He added that investigations have revealed that Ulfa (I) had hired a few people to execute both the blasts and the police have identified most of them involved in the process of transporting the explosives to the district, acting as local guides to trigger off the explosions and the like.

The SP said the police could not collect the suspects' photographs but contacted the people who knew them. He said these people have provided the descriptions of the suspects to Banerjee, who made the sketches. He said the sketches, which are expected to be very useful in tracking down the suspects, will be distributed among people.

Banerjee told The Telegraph over phone from Tinsukia that he had visited Assam several times to assist in various cases and this time too he is doing his job. Banerjee said he has drawn the suspects' sketches on the basis of the descriptions he got from the persons who are believed to know them.

"I shall be able to finish my job in a day or two and return to Calcutta," Banerjee said.

As part of the increased security measures in the aftermath of the blasts, the police have started installing CCTV cameras in Tinsukia town. Nine vulnerable points, like markets and important intersections, have been selected and two cameras have been installed.