Sources said that one of the terrorists who bombed the main shrine, had been caught on CCTV carrying a heavy rucksack containing three gas cylinder devices in the wee hours of July 7.
There was no evidence of any guard nearby. While the NIA has released the bomber's sketch on the basis of the descriptions by resident Sri Lankan and Thai monks, the footage shows the terrorist had slipped on the monk robe over his jeans and T-shirt. It was later found discarded at the sanctum sanctorum.
The security agencies had earlier suspected the involvement of Myanmar's Rohingya Muslim activists in the attack, but there is to date no evidence of any Rohingya group's involvement in terror activities.
"We suspect a new IM module in Assam as the North-East could be a new hideout for the group with enough opportunities to radicalise Muslims in the name of atrocities on them by Bodos in 2012," said a senior official.
Using the three unexploded devices, the investigators traced the gas cylinder manufacturers in Meerut, with distributors in Patna. It was also discovered that a Rajkot-based unit had produced a batch of 300 Lotus Diamond clocks and sold these in Assam.
Two dealers in Guwahati's Fancy Market had purchased these clocks and one of them sold 13 clocks in a single day in August.