Records of calls made from cellphones of suspects Kamal Ansari and Khalid Aziz Sheikh, arrested along with another suspect in connection with the recent serial blasts, would be the key to future investigations in the blasts, ATS sources said.
Ansari and Sheikh, both residents of Madhubani district of Bihar and arrested by the Anti-Terrorist Squad on Friday, were suspected to have provided logistic support in the blasts, sources said.
"Investigation suggests that both were in Mumbai for some days prior to the blasts, and left for their native village soon after the blasts," an ATS official said.
The contact list on the cellphone seized from Ansari was being scrutinised, while the cell phone service provider had been asked to furnish details of the calls made from the cellphones of both suspects.
Besides Ansari and Sheikh, ATS has also arrested Mumtaz Ahmed Maqbul Ahmed Choudhary, brother-in-law of Ansari who stays at Turbhe in Navi Mumbai.
Sources said that Choudhary was being independently interrogated as he was suspected to have provided shelter to a group of friends of Ansari before the blasts.
The sketches prepared by the ATS were being verified with the help of Choudhary, while a possibility was being explored if Choudhary was willing to cooperate to provide details of other persons who stayed at his house, so that their sketches too could be prepared, ATS sources said.
Meanwhile, the forensic test report of the black powder seized from Ansari's house is expected to arrive on Saturday evening, sources added.