The Arab Contractors Company began on Saturday fixing the damages that happened at a Cairo security office as a result of a bomb explosion on Friday, a state website said.
A team was formed on Friday to weigh the damages as other bombs went off across the country, rising the death toll to six people on the eve of January 25.
Egypt's Islamic Museum in Old Cairo was also damaged in the blast that injured at least 76 people.
A militant group that goes by the name Ansar Bayt al-Maqdis (Supporters of Jerusalem) has taken responsibility for the attacks, but the Muslim Brotherhood is widely blamed by the media and many Egyptians.
Egypt stepped up security on Saturday ahead of gatherings by rival groups to either protest against the army or celebrate the third anniversary of Hosni Mubarak's ouster.
A bomb went off on Saturday morning, wounding one person.