They are likely to question 45 persons lodged in the Sabarmati jail in connection with several incidents including the 2008 Gujarat blasts.
Operatives like Adnan, Safdar Nagori, Peedical Shibly and Shahduli Abdul Karim among others are termed as the prime accused in this case.
These are the same people who broke away from the Students Islamic Movement of India and launched a separate radical outfit that later went on to become the Indian Mujahideen.
After breaking up with the SIMI these men met at Ujjain in Madhya Pradesh.
A training camp was later organised at Vagamon in Kerala.
According to the National Investigation Agency, at this camp they were able to lure at least 300 cadres for their cause.
In 2007, 45 members of the SIMI headed by Nagori met at Castle Rock in Hubli, Karnataka. This is where they planned the attacks in Goa, Gujarat, Delhi and Bengaluru.
The Sabarmati jail tunnel case is interesting because each accused was part of the launch team of the radical SIMI. Also, each one had a role to play in the Gujarat blasts and is facing trial.
Police sources say the plan to escape from jail was hatched in November 2012.
The role of the Islamic Chattra Sangh is also being probed.
The ICS was named for the first time when Kerala operative T Nasir was arrested. He had revealed that it was the front group under which they operated and had links to Bangladesh.
According to the Intelligence Bureau, the ICS was in touch with members of the SIMI, who provided them with funds and information on escape routes to Bangladesh.
The Gujarat Police feel that Adnan, a resident of Hubli and a civil engineering student, was the mastermind of the plot. It is alleged that the plan was hatched by Adnan in Bengaluru last year.
The police have not been able to establish who he met on his visit and how the members of the ICS got in touch with him.
Digging a tunnel in a high security prison was an act of desperation say police officers.
The hanging of terrorist Ajmal Kasab had shaken them up.
Their plan was to dig a tunnel from the jail to the outside and hide in the nearby forest before fleeing to Bangladesh with the help of the ICS, sources say.
Investigators have not ruled out the possible involvement of insiders in the escape plan.
The accused had access to shovels and pickaxes, and worked in batches of 14 to dig the tunnel. Jail authorities have, however, claimed that spoons and dishes which were used for digging. They too are being questioned in the case.
NIA explores Bihar link to Hyderabad blasts
Delhi HC blast: Wasim Malik charged with waging war
Hyd blasts probe: Stop witch-hunting, say rights groups
Ishrat case: Police officers' custody extended till Feb 28
Govt to launch Rs 10 plastic notes in 5 cities