The police said on their way back to the orphanage from school, the girls would be offered treats, cajoled, taken to a shop and then sexually assaulted. The girls were threatened and warned against complaining to anyone.
A guard who saw a girl being taken out of the shop one day grew suspicious and informed the orphanage, which filed a police complaint on Saturday.
Investigations have confirmed that seven minors had been sexually abused for two months by the men.
They have been charged with rape and under the stringent POCSO (Protection of Children Against Sexual Crimes) Act.
There is also a suspicion that more girls were assaulted by the group.
The accused men were questioned till late night on Monday.