© ReutersAn Iraqi official carries a ballot box, after a fire at a storage site in Baghdad on June 10.
The June 11 report said the suspects included three police officers and an employee of Iraq's elections commission.
The June 10 blaze destroyed a warehouse containing ballots from Baghdad's Al-Rusafa district, ahead of a recount of votes cast during the country's legislative elections last month.
Authorities said the ballot boxes were saved, but a member of Baghdad's provincial council said that "all the boxes and papers have burned."
"There is no doubt that it was a deliberate act and I am personally following up on the investigation with the criminal police and the committee tasked with probing the fire," Interior Minister Qassem al-Araji said.
Prime Minister Haidar al-Abadi described the fire as a "plot" aimed at undermining Iraq's democracy.
Amid allegations of widespread fraud, Iraq's parliament last week ordered a manual recount of some 10 million votes cast during the May 12 polls, which were won by an alliance headed by Shi'ite cleric Muqtada al-Sadr.
Comment: See also: Ballot box blaze: Iraq's largest voting warehouse goes up in flames