The accused, identified as Bunty Jahangirdhar (40), a resident of Ahmednagar district of the state, was picked from his residence by the investigators for interrogation.
After thorough interrogation, he was placed under arrest on Sunday.
He was on Monday produced before a MCOCA court which remanded him in police custody till January 24.
"Jahangirdhar was a part of the conspiracy hatched to trigger the blasts," a senior ATS official told PTI, without divulging further details saying that a probe was on.
Earlier, Maharashtra ATS had arrested seven alleged Indian Mujahideen operatives - Firoze Sayyed, Irfan Landge, Imran Khan, Asad Khan, Sayyed Arif alias Kashif Biyabani, Munib Iqbal Memon and Farooq Bagwan - in connection with the blasts.
Four co-ordinated low-intensity explosions struck the busy arterial road in the heart of the city on August 1 last year raising the spectre of terror.
The explosions occurred at Jangli Maharaj (JM) road at spots near Balgandharva Theatre, Dena Bank branch, McDonald food outlet and Garware bridge. The first explosion took place at Balgandharva Theatre in which one person was seriously injured.
The explosion outside McDonald occurred in a dustbin while the blasts near Garware bridge and Dena Bank were reported from a cycle which had a bucket with explosives strapped on, police said.
The ATS had invoked the stringent Maharashtra Control of Organised Crime Act (MCOCA) against the seven accused recently. Jahangirdhar was also produced in the same MCOCA court.