According to Arun, though the electronics and explosives used are the usual ones, it is the welding that is causing uniqueness and worry. "We have a lead from Haldwani which is being followed up," Arun said. "It appeared to be some kind of crude bomb made by local firecracker experts, who used an intricate welding process," a police source added.
Local welders have been contacted and more than a thousand mobile numbers around the vicinity of the explosion are being screened, sources said.
The National Security Guard, National Investigation Agency, Anti-Terrorism Squad, Special Task Force, Intelligence Bureau and forensic lab have still not reached to definite conclusion in the case.