The arrested suspect has been identified as Tabish.
Based on leads provided by Imtiaz Ansari, who was arrested in connection with the blasts, the police picked up Tabish from Motihari district in Bihar.
The police have named Ansari, the man who was arrested from the Patna railway station, the site of Sunday's first blast, as the mastermind of the strike.
Ansari is one of the six men named in the FIR that also names his mentor Tehseen Akhtar, reports said.
The police said that Ansari could be part of a newly formed module of the terror group Indian Mujahideen in Ranchi set up by Akhtar and wanted to create panic and trigger a stampede that could cause many deaths.
The police on Tuesday found three more live bombs from Gandhi Maidan, the site of Bharatiya Janata Party (BJP)'s Prime Ministerial candidate Narendra Modi's rally in Patna that was targeted by militants on Sunday.
The bombs were defused by security forces who were quoted as saying that at least one of the three was very powerful and could have caused greater damage.
Six people were killed and over 80 others were injured in a series of crude bomb explosions before Modi's Hunkar Rally at Gandhi Maidan in Patna.
--IBNS (Posted on 30-10-2013)