While Mansoor Peerbhoy -- who allegedly sent IM's e-mails ahead of the terror attacks in Delhi and Ahmedabad -- has been arrested by the Mumbai [Images] police, Abdul Subhan, Riyaz Bhatkal, Iqbal Bhatkal, Qayamuddin and Shadab Malik are still out there, likely planning their next attack.

Intelligence Bureau officials told rediff.com that these men matter most if the investigations into this year's terror attacks have to progress. Terror groups work on a need-to-know basis and hence, it is almost impossible to elicit complete information about the terror operation from the foot soldiers who have been arrested so far.

Abdul Subhan, for instance, could provide important leads into the IM's operations, even about any role the organisation may have played in the Mumbai attacks, IB sources say.

The IB suspects Subhan may have slipped into Pakistan.

Another big catch would be Riyaz Bhatkal, who took charge of the IM's financing at the Lashkar-e-Tayiba's [Images] behest. While some sources suggest he too may be in Pakistan, other investigators believe he is still in India.

IB sources say Bhatkal, who has close Lashkar ties, could shed light on how the Mumbai attacks were financed. He raised funds and handled Lashkar operations in south India before he was re-assigned to the IM. The Lashkar wanted his assistance to ensure IM's growth.

Investigations into the Hyderabad blasts of August 2007 also suggest Bhatkal's hand.

Another man on the run is Qayammuddin, a key member in the outlawed Students Islamic Movement of India. From him, the investigators believe they could secure information pertaining to the terror trade route.

Iqbal Bhatkal, Riyaz's brother who helped set up terror modules in south India, is suspected to be still in India.

Shadab Malik assembled the components for the bombs used in the Delhi [Images] blasts. He is said to have collected the material from someone only known as 'Sharukh Khan', likely a false name.

'Sharukh Khan', according to the police, had a bomb factory in Karnataka, which supplied improvised explosive devices to the IM.

When these terrorists are arrested, the law enforcement agencies will obtain crucial insights on the terror modules operating in north and south India. While the northern module is known as the Mahmood Ghaznavi brigade, the southern module is known as the Shahabuddin Ghauri brigade.