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.
The bombs were found at Gandhi Maidan even as police named Imtiaz 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, media reports said.
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 cause panic and trigger a stampede that could cause many deaths.
Earlier, Union Home Minister Sushilkumar Shinde on Tuesday said Chief Minister Nitish Kumar's Bihar government was alerted about a possible attack on Modi's Hunkar rally.
"Whenever there are such rallies happening, the states are given specific inputs in advance. An input was given to the Bihar government on the Patna rally too," Shinde told reporters.
"We have issued alerts to all states with regards to the political rallies and have asked them to be alert.
"We send specific alerts as and when we get them. State police must be alert while rallies are being organised," he said.
With Shinde facing criticisms for attending music release of a Bollywood film hours after Bihar serial blasts, External Affairs Minister Salman Khurshid defended him and said he has a "life beyond Patna".
"Mr. Shinde has a life beyond Patna. What happened in Patna was abviously very sad. Lives were lost because somebody is plying awful kind of politics," Khurshid told media.
He took a dig at Modi for not mentioning about the incident during his speech at his Gandhi Maidan rally in Patna.
"You can criticise Mr. Shinde for carrying on life as usual but nobody has asked questions why did nothing happened to Mr Modi? He went on with his speech. Not a word about the people who died, not a word about what had happened. Because it was not in the script," said Khurshid.
On Sunday, Shinde launched the music of actress Kangna Ranaut's upcoming film 'Rajjo' hours after serial blasts
The BJP on Monday said the Bihar government was warned that there could be some sort of terror strike in Patna city for Modi's Sunday rally.
Leader of Opposition in the Rajya Sabha and senior BJP leader Arun Jaitley told NDTV: "My sources also tell me that there was a general alert on October 1, a specific alert on October 23 on Indian Mujahideen with regards to Hunkar rally."
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 city.
"I was told by Gujarat police officer present there that the Bihar police was reluctant about advance security liaison. The security was callous and casual, inadequate,"Jaitley told the channel.
--IBNS (Posted on 30-10-2013)