Egypt's security forces have since 2014 been battling an Islamic State affiliate in northern Sinai, where militants have mostly hit police and soldiers but also occasionally targeted infrastructure and businesses.
Two security sources in al-Arish, the area capital, said armed men attacked the convoy, which was carrying coal to a cement factory.
The bodies of the truck drivers, all shot to death, were taken to the morgue of Suez public hospital, four medical sources said.
A military spokesman said there was no official statement. An interior ministry official did not respond to a request for information.
No group immediately claimed responsibility for the attack.
"They have threatened us repeatedly, asking that we don't work for the army's companies. We informed the factory management of the threats and asked them for more protection," one local truck driver, Ismail Abdel-Raouf, told Reuters.
Hundreds of police and soldiers have been killed since the insurgency quickened pace in northern Sinai after the 2013 ouster by the military of then-president Mohamed Mursi of the Muslim Brotherhood during massive protests against his rule.
A home-grown jihadist group, Ansar Bayt al-Maqdis, declared allegiance to Islamic State in 2014 and has since tried to spread outside the peninsula by targeting Christians with attacks on churches on the mainland.
Two security sources in al-Arish said armed men attacked the convoy
Suspected militants shot dead at least nine truck drivers in Egypt's Sinai region late on Thursday when they targeted a transport convoy, setting the vehicles on fire, medical and security sources said on Friday.
