Five improvised bombs exploded early Tuesday in Cairo's Matariya district in an apparent targeting of Vodafone and Mobinil mobile-phone stores, the latest in a series of attacks which affected the communication shops.
The bombings, which caused no casualties, damaged ten private cars and seven shop facades on Matariya's main street.
The prosecutor's inspections at the sites of the explosions on Tuesday, two of which were at Vodafone and Mobinil, could not retrieve CCTV material to assist in the investigation.
Ahram Arabic news website reported that CCT systems had been down at the Vodafone store for three days, while Mobinil did not have a camera system in place.
Initial police investigations said unknown assailants planted the bombs beneath private cars in the area.
The bombs reportedly contained a total of five kilograms of explosive material.
Egypt has recently seen a spike in bombings in civilian areas after months of attacks almost exclusively targeting police and army personnel and facilities, mostly claimed by Islamist groups.
Explosions in the working-class district came hours after two small bombs hit separate spots also in the capital late Monday, also with no casualties.
Earlier on Monday, a blast outside the High Court complex in downtown Cairo left two civilians dead and at least nine people injured, including police officers.
On Thursday, five bombs detonated in Giza killing one and injuring at least nine people, with four of them seemingly targeting mobile-phones stores of Vodafone and Etisalat.
Matariya has been the scene of weekly confrontations between supporters of ousted Islamist president Mohamed Morsi and police for months.