Even as investigations continue into the Pune blast of February 13, the police are also looking at the possibility of some right-wing groups being involved in the attack.

"We do not want to leave out any aspect pertaining to the investigation and there is no harm in checking every angle to it," an investigator told rediff.com. He also said they had significant leads on the Indian Mujahideen's [Images] involvement in the blasts.

Sources say the reason behind the police probing the right-wing groups is due to the huge presence that such groups have in Maharashtra [Images], especially Pune. One right-wing group which was involved in the Malegaon blast case had shown that it had the capability to procure RDX. The prosecution which was dealing with the case had stated that one of the leaders of this group, Col Srikant Prasad Purohit, had managed to steal RDX, that had been seized, during his stint in the army.

Intelligence Bureau sources pointed out that in the earlier cases, each blast had a unique 'signature'. However now, terror groups have a tendency to change their signature in each blast. This makes it difficult to track the bomb-makers and establish patterns behind the blasts.