Wairoa Police Senior Sergeant Tony Bates feared naming the victim's hometown would identify her to the attackers. The robbery was a concern for the community, he said.
"It's a concern these children have conducted these types of activities," he said.
"Now they have just got to complete the processes going on and hopefully that will sort it."
Five of the offenders were due to appear in the Wairoa Youth Court on charges of aggravated robbery, with the remaining four referred to Youth Aid.
Wairoa Mayor Les Probert said the behaviour was a national issue, and the town had processes in place to deal with gangs.
"At every place in New Zealand at this time of year these things go on," he said.
"These things are happening and we don't want them to happen. It is the sort of thing we are attempting to avoid."
He said the council liaised with police regularly, and had youth programmes.
"We have meetings with the police, we had a meeting just before Christmas and have acts in place to deal with [gangs], unfortunately the police can't be everywhere at the same time."
On Monday, a 24-year-old man with no gang connections was viciously stabbed and beaten in Napier as he walked home from New Year's Eve celebrations with a friend.
Police believe the three offenders could have been associated with the Black Power gang, and attacked the victim because he was wearing a red T-shirt - the colours of rival gang, Mongrel Mob.