New Delhi:  Investigators have fanned out across India to check out several leads available from the Mumbai attacks. The information gathered so far indicates the existence of a massive secretive network with tentacles in Delhi, Kolkata, Bangalore, Dhaka, and elsewhere.

In Delhi and Kolkata, investigators are trying to find out who bought the SIM cards that were later recovered from the slain terrorists in Mumbai. Sources said the Kolkata police have identified at least two youths who may have bought SIM cards in West Bengal. They are believed to have bought the cards from three different places using a fake voters identity card in the name of Hossain Ur Rahman. In Delhi, investigators are looking at shops in Karol Bagh from where the SIM cards were bought.

The jigsaw being put together suggests the terror attacks mounted by Pakistan-based youths had strong support from a homegrown network. The same network may have been involved in recent strikes. Though it is not a cohesive group, the network comprises several former Simi (Students Islamic Movement of India) members with a strong base in Hyderabad and other parts of South India. The group has deep linkages with the Lashkar-e-Taiba, which has since denied involvement in the attacks. This group is influenced by Taliban and al-Qaeda ideology.

Suspicions about this group, which for some time has been calling itself Indian Mujahideen, have been firmed up by links emerging between the latest Mumbai attacks and the 2005 attack on the Indian Institute of Science, Bangalore.

The networks of Shahid Bilal, a Hyderabad resident who was killed in Pakistan some time ago, and Riazuddin Nasir, his close associate who was arrested in Karnataka, had joined hands with a faction of Simi and other like-minded youths to create a network of India's most formidable terror supporters. This group is believed to have carried out several bombings in Indian cities and assisted in the attacks on the IISc, mostly under the banner of Indian Mujahideen. The Mumbai attacks were carried out under the banner of Deccan Mujahideen.

Sources said Abu Hamza, who escaped after the December 28,2005,attack on the IISc, was a key motivator for the 10-member terror group that attacked Mumbai. They were convinced by Hamza that it was easy to fool the Indian police and escape back to Pakistan, according to arrested terrorist Ajmal Kasab, now in the custody of the Mumbai Police.

Investigators believe that the Lashkar-e-Taibas Dhaka-based operatives obtained the Indian SIM cards and supplied them for use during the attacks. The terrorists were also provided with SIM cards from Austria and the US. Besides, several GPS systems and a Thuraya satellite phone were in the possession of the terrorists, according to a source.

The investigators are also combing through several leads pointing to the possible involvement of the underworld, especially smuggling gangs, in organising logistical support for the terror group. The customs department has for the past few months been investigating the massive smuggling of diesel and other items by a group of Dawood Ibrahim henchmen, especially one led by a Colaba-based customs clearing agent. His son and the sons employees are being investigated.

As of now, the most noticeable challenge for the investigators is to find out the extent of local support made available to the terrorists. "We still havent made a breakthrough," said a senior official. He said unless the local contacts are unearthed, it would be difficult to get at the full truth behind the conspiracy.