She was kept home from school after sustaining the facial injuries, police say. When officers visited her home, the girl was allegedly instructed by family members to cover up with a burqa that left only her eyes exposed - a covering the girl told police she would not usually wear. At school, she wore a head scarf.
She was absent from school long enough for a friend to become anxious about her whereabouts, police say. When the friend learned of the abuse through community networks, she called the police.
"At this stage it is clear that a number of members of the community were aware of the extent of the abuse and did not seek medical assistance for her injuries or alert authorities," Ms Boniface said. "This included people who were in positions of trust and who should have been relied upon to provide help."
Police believed that family members were also instructed to lie to investigators about the abuse, and did so out of fear for their own safety.
Officers learned about the abuse in early November. The girl was removed from her home by Child, Youth and Family and placed in "secure care" with another Muslim family. No one has yet been charged, although police say arrests are likely.
She recently completed her school exams, Ms Boniface said.
Detective Inspector Jim Gallagher, a police field crime manager, said people needed to speak up about child abuse. He praised the bravery of the school friend who called police.
"When you know about a child that possibly could be at risk, then that warrants you making it your business. If you do nothing, then no one will ever know. It's a child's life you're gambling with if you don't report it."
Javed Khan, acting president of the Federation of the Islamic Associations of New Zealand, said the offending could not be tolerated. It was likely a one-off case, he said.
"Maybe the family members were trying to hide it, but I don't think the community would condone anything like that. If we became aware of it we would definitely bring it to the attention of the authorities.
"We are subject to the laws of the country and follow the laws of New Zealand. Anything like that is not accepted here. It has nothing to do with Islam or the religion. It's more to do with a cultural thing ... It could just be the family."
• Since 2007, it has been illegal for any person - including parents - to use any physical force on a child, including for the purposes of correcting behaviour or as a form of punishment.
• In the year to June 30, police investigated almost 90,000 family violence cases. There were children present in more than 56,000 of those.
Help is available to victims of physical and emotional abuse. Victims, or anyone aware of the abuse of others, should contact any of the following services for assistance.
Police: 111
Crimestoppers (anonymous tipline): 0800-555-111
Child, Youth and Family: 0508 FAMILY (0508-326-459).
Shakti (support for domestic violence victims in the Asian, African and Middle Eastern communities): 0800 SHAKTI (742584)