The officials say the explosives were leftover munitions, but they couldn't provide more details about when or why the bomb was planted. They say Wednesday's explosion occurred some 500 feet (150 meters) from the pyramids outside Cairo.
The officials say the explosion was triggered by peddlers who saw metal glinting out of the sand and began hitting it with iron sticks, thinking the casing might conceal valuable goods. Three of them were seriously wounded.
The officials spoke on condition of anonymity because they weren't allowed to release the information.