The incident started when four workers at the plant were cleaning the sewer in Meit Kanaa village, Qalyubia governorate, and fell into it, al-Ahram reported Wednesday.
The rest fell in while trying to save the workers.
Health officials in Qalyubia said that all the victims died of suffocation.
'SNL': 'Anchorman 2' cast, One Direction sing 'Afternoon Delight' [VIDEO]
Wisconsin business offering 'therapeutic cuddling' forced to close