"A suspected accused (who was) seriously injured in bomb explosion while fitting a timer at Patna railway junction died late Sunday night," Patna Senior Superintendent of Police Manu Maharaj said.
Officials at Patna Medical College and Hospital, where 83 injured in serial blasts were admitted Sunday, said that at present 38 are undergoing treatment.
Five are in critical condition and others have been discharged, officials said.
Security was tightened in the city a day after six bombs exploded in and around the Gandhi Maidan where Bharatiya Janata Party's prime ministerial candidate Narendra Modi addressed a rally hours later and a blast took place at the railway station.
Additional security forces have been deployed at all important places including crowded markets to instil a sense of confidence among local people, who panicked after the serial blasts, Additional Director General of Police (Law and Order) S.K. Bharadwaj said.
He said that the attack was the first in the history of Patna.
Maharaj said that National Investigation Agency (NIA) team, which has begun probing into the serial blast, Monday sealed the Gandhi Maidan.
The NIA team hopes to collect more evidence from the ground.
Another senior police official said that a total of 13 suspected people have been detained including a seriously injured youth from the ground after serial blasts.
"All of them have been interrogated by the Bihar police, NIA and IB officials," he said.
The first of the supposedly low intensity blasts ripped through a toilet at around 10 a.m. at the newly built Platform 10 of the railway station in the heart of the city, killing one person and wounding another.
After an hour, by which time Modi had reached Patna but not the rally ground, four explosions took place inside the Gandhi Maidan, killing four others and causing a lot of panic, police and witnesses said.
The Patna railway station is located two-three kilometres from the sprawling Gandhi Maidan.