The NIA is in the process of identifying all the six people who were part of the 22-minute video aired on Friday last and later taken off.
Some of them are from Maharashtra and one or two are part of the Azamgarh module, official sources said, adding help of an arrested Islamic State operative Areeb Majid was being taken to identify them.
One of the men in the video has claimed that he was at Batla House when police had raided the premises and fled afterwards.
However, it was not clear whether he was there inside the same house where two alleged Indian Mujahideen militants were killed in an encounter in September 2008, the sources said.
Engineering student Fahad Tanvir Sheikh, a resident of Thane, who travelled to Syria in 2014 along with three other men from the city, has been identified "conclusively" in the video. He has been charge-sheeted by the NIA in absentia under various sections of IPC and Unlawful Activities Prevention Act (UAPA).
As the process of identifying those in the video was underway, the sources said there was a suspicion that some of them were part of banned Indian Mujahideen before they joined ISIS after snapping ties with their Pakistan-based leadership.
Several IM cadres are believed to have joined ISIS since 2014 after they rejected the leadership of its Karnataka-born chief Riyaz Ahmad Shahbandri, also known as Riyaz Bhatkal.
The men include a former Mumbai hospital employee Abu Rashid, Shahnawaz Ahmad, a Unani doctor and the son of a local Samajwadi Party politician in Uttar Pradesh’s Azamgarh, and students Mohammad Bada Sajid and Mirza Shadab Beig.
Karnataka's Muhammad Shafi Armar, one of the Indian Mujahideen fugitives, has been named by the NIA as a key online recruiter of Indian youths for the Islamic State.
The 22-minute video, which is mainly in Arabic, says 'Jihadis' from 'Hind' wal 'Sindh' (India and Pakistan) "will soon take revenge”.