An official source in Minya said that police forces securing referendum committees in the governorate found five improvised bombs inside four committees in the Beni Mazar neighborhood.
Police and explosives experts moved in to inspect the bombs.
Another bomb had exploded earlier Tuesday outside North Giza court, just hours before the referendum started.
The total number of eligible voters in the referendum is 52,742,139 voters, spread over 30,317 sub-committees, while 13,867 judges are monitoring the project.
Voting starts from 9am until 9pm on Tuesday and Wednesday, 14 and 15 January.
Edited translation from Al-Masry Al-Youm