Egyptian security authorities on Thursday detected three rockets in Sheikh Zewayed, 15km from the border with Gaza.
An official security source at the North Sinai Security Directorate told the Aswat Masreya news website that "the rockets are medium sized and of unknown calibre. They are operational."
The rockets would have been smuggled to Gaza through the Rafah tunnels, he said.
An explosives team deactivated the rockets, he added.
Egyptian Foreign Minister Mohammed Kamel Amr announced the cessation of hostilities between Israel and Gaza at a joint press conference in Cairo with US Secretary of State Hillary Clinton on Wednesday.
A ceasefire took hold on Thursday in and around Gaza after a week of cross-border violence between Israel and Palestinian resistance groups that killed at least 160 people.
The Sinai Peninsula, a largely desert area bordering Israel, has been the site of several attacks on Egyptian security forces in recent weeks.
On 3 November, three policemen were killed and three were injured near the Egypt-Israel border.
A few days later, on 6 November, a senior officer from the Ministry of Interior's General Security section was seriously injured after being shot in the jaw and arm by unknown assailants.
On 11 November, an unknown armed group fired at the Central Security Forces camp in the Ahrash district of Rafah in North Sinai.