Investigating officers told rediff.com that that Lashkar has three such units in India. The Shahabuddin Ghouri Brigade operates in southern India.
IB sources said the Mahmood Ghaznavi Brigade operates in north India.
The third unit is known as the Al-Zawahiri Brigade, a name inspired by the Egyptian doctor who is the number two man in Al Qaeda, Ayman al-Zawahiri.
After the arrests in connection with the Bengaluru blasts, it was confirmed that the Shahabuddin Ghouri Brigade was based in Kerala.
Intelligence Bureau reports suggest that while the Shahabuddin and Ghaznavi Brigades are under the Lashkar-e-Tayiba's direct control, the Al-Zawahiri Brigade is a specialised unit which only undertakes suicide attacks.
The Shahabuddin and Ghaznavi Brigades concentrate on serial blasts, planning, recruitment and training of its terror cadres. Both groups are suspected of having around 1,000 members.
The Al-Zawahiri Brigade is said to have 30 members.
Although the Lashkar has divided its operations, all three brigades report to the same man, the Lashkar's Riyaz Bhatkal. The Indian Mujahideen's Abdul Subhan is said to be his second in command.
