"Kafeel has been sent to ATS custody till June 8," said Maharashtra Anti-Terrorism Squad (ATS) chief Rakesh Maria.
Ansari (55), who was in the custody of Delhi Police in a terror-related case, was arrested in the Mumbai blasts case on May 19 and is accused of criminal conspiracy, aiding and abetting the explosions and providing logistical support in executing the crime.
Ansari, hailing from Darbhanga district of Bihar, was earlier remanded in police custody till May 29.
Twenty-seven people were killed and 130 injured when three explosions ripped through the crowded areas of Opera House, Zaveri Bazaar, and Dadar (West) in Mumbai on July 13 last year.
The ATS had earlier arrested four accused, Naquee Ahmed, Nadeem Shaikh, Kanwar Pathrija and Haroon Naik in the blasts case. The charge sheet against them was filed on May 25 in a special court of the Maharashtra Control of Organised Crime Act (MCOCA).
Ansari, a "close aide" of Yasin Bhatkal, had been nabbed in February by a team of Delhi Police's Special Team from Darbhanga.
