The two mortar shells landed in the vicinity of the governorate headquarters. No injuries were reported, according to the state news agency MENA yesterday.
The police and army personnel are searching the area for other explosives.
North Sinai has been the scene of many violent attacks by Islamist militants since the January 2011 revolution. The attacks targeting police and military increased after the ouster of Islamist ex-president Mohamed Morsi last year. Over 500 policemen and soldiers, have been reportedly killed in the attacks.
The explosion cause by the two mortar shells came days after residents of Rafah on the border between Egypt and the Gaza Strip have begun evacuating their homes after an official decision to form a buffer zone.