Sanders, who has been in custody since October and looked gaunt when he made a brief appearance before Judge Keith de Ridder on Tuesday was further remanded in custody to August 19 for a review of the new charges. Judge de Ridder also set a date of October 24 for a pre-trial hearing. No application was made for bail.
Most of the original 25 charges are of indecent assault, but they also include two of sexual violation and one of assault on a child.
Kaitaia detective Mark Dalzell, who is heading the enquiry, said on Tuesday that he still wanted to hear from anyone who had any relevant information and had yet to speak to police. He was pleased that 13 complainants had had the courage to come forward, but feared that there could be more.
"If you know something, come forward and talk to us," he said.
"There could well be more victims who have chosen not to complain or become involved.
"It's only by speaking out that people like this can be stopped, and we can do our job of stopping them."
Detective Dalzell can be contacted at the Kaitaia police station, phone (09) 408-6500, or call Crimestoppers, anonymously, on 0800 555-111.