Two young girls have reported being sexually assaulted by boys while in state care in Upper Hutt.
The girls, one aged 12 and the other around 13, were living in the same state home.
The mother of the 12-year-old said she complained to police last September and little had been done.
Police investigated both complaints but said there was not enough evidence to prosecute, though the case of the 12-year-old remained active.
Her daughter had been placed in the home in July by Child Youth and Family, now the Ministry for Vulnerable Children/Oranga Tamariki, and had been under the agency's care since March.
She left the house where she'd lived for two months following the reported assault to get back to her family 30km away.
"My daughter came running home telling me she was raped," her mother said.
"She said her and this other girl ended up getting led out of the house to a nearby property - empty field.
"These two boys came in. They were put there for the weekend or something. One was 16 and the other was 14. I believe what she said was true."
She said she immediately called the police, but they took the girl back to the same Upper Hutt house.
"I sort of thought: 'Actually no, you've got to look for a safer place for her to be right now. This has all happened there'.
"The social worker said, 'Sorry that's the only placement we have at the moment.'"
The girl ran away from the home 15 times in the two months following the reported assault, often heading to her mother's house.
The mother had lost custody of her daughter after admitting beating her with a steel pole in January 2016, and is going to the Family Court next week to get her back.
A second girl also reported being sexually assaulted by a boy living at the same Upper Hutt state home in December.
The mother of a boy who had lived at the house at the time said her son faced accusations over both assaults.
"He remembers one occasion when they were out sort of in the park late at night," she said.
"He left and these young children were on their own. He's not sure what happened, but he indicated anything could have happened because lots of kids frequent the area."
'Family homes, not secure residences' - ministry
In a statement, the Ministry for Vulnerable Children said the Upper Hutt home was being run as a girls-only facility at the time of the 12-year-old girl's complaint.
The accused boy was living at another of its homes elsewhere in Wellington, it said.
"These are family homes - they are not secure residences. Young people can have access to their social groups. The young people don't always make the best choices regarding their friends," it said.
"These young people do not spend all of their time at homes and it is not possible to monitor them every minute of the day."
The ministry said at the end of 2016, the Upper Hutt home had security guards and overnight supervision by an after-hours social worker to mitigate the risk of young people absconding.
It is reviewing the supervision of family homes in the Wellington region.
The ministry was asked if there had been other allegations of sexual assaults at the Upper Hutt home in recent years, but it said it did not know because details were held in individual case files.
Detective Senior Sergeant Neil Holden, from Wellington's Child Protection Team, confirmed police investigated two reports of sexual assault between "peers" at a Ministry for Vulnerable Children/Oranga Tamariki home.
He said the 12-year-old's case, reported on 22 September last year, was still open.
"Difficulties arose in being able to conduct a formal interview straight away. This was due to the child running away and being unwilling to speak to police," Mr Holden said.
"A formal interview of the girl was undertaken on 8 November and the following day she was medically examined. Police have made every attempt to obtain further information that would assist in the investigation."
Mr Holden said the second girl was also interviewed and examined, but there was insufficient evidence to prosecute.