The state-run news agency did not provide full details of the infractions on Thursday, but cited an Interior Ministry statement made by an election observer that said some of the arrests were linked to distribution of CDs and other materials.
It said about 20,000 pamphlets distributed as election material had been confiscated because, under Iranian law, it is illegal to make unsubstantiated charges against a political rival during the campaign.
A total of 148 claims of violations were reviewed by a joint committee comprising intelligence, police and judicial officials. At least 44 were linked to "military personnel", the report added.
The report came just hours after Rafsanjani said on state television late on Wednesday that "violators of the elections misused public fund to distribute millions of CDs against me and, unfortunately, officials have not decided what to do about them yet ... I hope they will be treated according to the law".
Ayat Allah Akbar Rafsanjani faces Ahmadinejad on Friday in Iran's first head-to-head presidential ballot.
Rafsanjani was shaken in the first round with Ahmadinejad right on his heels – 21% to about 19.5%.
The investigation report added that a "military person" was also among those arrested.
No other details were given, but a statement from Iran's armed forces said none of its personnel was implicated, which may indicate that a member of the Revolutionary Guards or the paramilitary "Basiji" was involved.
A shopkeeper tapes an
Ahmadinejad poster to his window
The third-place finisher, former parliament speaker Mahdi Karroubi, claimed the Revolutionary Guards intimidated voters to cast ballots for Ahmadinejad.
He also accused the ruling clerics of overlooking other alleged violations such as multiple voting by one person.
Vote on Friday
Various political and social groups have set aside differences and tried to rally behind Rafsanjani, 70, who served as president from 1989-97 and later moved into a key post in the theocracy.
A series of street rallies in Tehran and elsewhere on Wednesday sent the message that Iran's hard-won social and economic reforms would be stifled by a populist Ahmadinejad -who has picked up significant working-class support with his blunt talk on economic and foreign policy issues.
But the Tehran mayor denies rumours he is seeking to bring back rigid laws from the years following the 1979 Islamic Revolution, such as segregation of the sexes.
The campaign period officially ended Thursday. But many newspapers, however, were filled with editorials against intolerance as indirect attacks against Ahmadinejad.