Union Home Secretary RK Singh said that the CCTV footage from Dadar, Opera House and Zaveri Bazaar was being scrutinised closely to try and spot the culprits who may have planted the bombs.
Forensic teams have already collected evidence like blood samples, explosive materials from all the three locations.
Till now no terror group has claimed responsibility for the blasts, but sources say the involvement of Indian Mujahideen cannot be rules out.
Almost 1 kg of ammonium nitrate was used to carry out the blast in Opera House, 400-600 grams were used at Zaveri Bazaar and 200 grams in Dadar.
The National Investigation Agency (NIA) on Friday conducted raids at the house of SIMI activist Manzar in Ranchi.
Though the Indian Mujahideen is the prime suspect in the Mumbai blasts case, the NIA sources have told CNN-IBN that the raids are not related to the Mumbai blasts.
Maharashtra Chief Minister Prithviraj Chavan on Friday made a startling revelation that he was cut off from his police force for almost 15 minutes after the triple blasts on Wednesday in Mumbai as the mobile networks were jammed.
The Maharashtra Anti-Terrorism Squad (ATS) on Thursday registered three cases in connection with the serial bombings that left 17 people dead and 131 injured.
The maximum casualty in Wednesday evening's terror attack was witnessed at Opera House where 10 people were killed.
Seven persons died at the explosion at Zaveri Bazaar, the police officer said. The third blast took place in Dadar.