A joint team of the railway police and the crime branch began investigations on Friday into a powerful bomb blast that ripped through a suburban train compartment on Thursday night in Mulund leaving 11 dead and over 65 injured.
Joint Commissioner of Police Javed Ahmed said the explosives used in Thursday's blast were similar to the ones used in last December's Ghatkopar bomb blast that left two dead.
Preliminary reports suggest that ammonium nitrate was used in Thurdsay's blast at the Mulund railway station.
Senior police officials, however, refused to comment on reports that the four bomb blasts in past three months in Mumbai were aimed at the city's Gujarati population.