The explosion damaged a windshield of another car, they said. Footage circulated online shows shattered windows of the bus.
Atif Moftah, general supervisor of the Grand Egyptian Museum, said the explosion did not cause any damage to the museum, in a statement issued by the Antiquities Ministry.
No group has immediately claimed responsibility for the attack. It is the second to target foreign tourists near the famed pyramids in less than six months.
In December, a bus carrying 15 Vietnamese tourists was hit by a roadside bomb, killing at least three of them.
Egypt has battled Islamic militants for years in the Sinai Peninsula in an insurgency that has occasionally spilled over to the mainland, hitting minority Christians or tourists. The insurgency gained strength after the 2013 military overthrow of the country's first freely elected president, an Islamist whose brief rule sparked mass protests.
- AP