According to Reuters, the bomb exploded as a patrol responsible for protecting a natural gas pipeline passed by, the sources said. No group has claimed responsibility for the attack.
The blast occurred southwest of provincial capital Al-Arish where two policemen were killed when their patrol car was struck by a rocket-propelled grenade three days ago.
Security forces face an insurgency that has killed hundreds of soldiers and policemen since the army toppled President Mohamed Mursi of the Muslim Brotherhood last year.
Most attacks occur in the Sinai Peninsula, which borders Israel and the Gaza Strip, as well as near Egypt's Suez Canal.
Security officials say Sinai-based militants are inspired by Islamic State. A senior commander from Ansar Bayt al-Maqdis, Egypt's deadliest militant group, has told Reuters that Islamic State has provided instructions on how to operate more effectively.
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