While it was initially believed that a local module from Mumbai helped carry out the operation, preliminary investigations reveal that the terrorists from Pakistan used two  modules to help carry out the attacks.

Intelligence Bureau officials probing the case along with the Mumbai ATS and who are simultaneously interrogating the lone terrorist in custody, Ajmal Kasab, have identified these modules to come from West Bengal and New Delhi [Images].

IB sources say the Lashkar e Tayiba, which masterminded the terror attacks on Mumbai, had deliberately avoided using a module from Mumbai as it would have left a trail which would have made the investigators' job easy. While the LeT has dedicated modules in New Delhi, in West Bengal it used modules reporting to the Harkat ul Jihad al Islami based  in Bangladesh. The LeT and HuJI share a symbiotic relationship.

In New Delhi, the LeT has around six modules while in West Bengal there are around 10 modules which are directly under the control of the HuJI.

These local modules played a key role in carrying out the terror strikes on Mumbai and members from these modules conducted a detailed study of the targets ahead of the actual attack.

Sources say these modules could have been working on the Mumbai strikes for the past year, and the series of blasts in the country conducted by smaller modules such as the Students Islamic Movement of India and other groups could have actually served to distract the security forces.

The IB says while the logistics were worked out by the local modules, they are still trying to ascertain who could have funded the operation. The Dawood Ibrahim [Images] link is under probe here, the IB says.

Both the Delhi and the West Bengal police are looking into the involvement of local modules, the IB says, and the latter is already on the job of finding out how the SIM cards used by the terrorists were procured from Bengal.