"The offending may be historic with the victims likely to have been boys aged 4 -15 years old at the time of the offending." Detective Matthew Lee said.
Police are asking for anyone with more information to come forward.
"We would like to reassure those who come forward that the information they provide us will be treated with sensitivity."
Anyone with information is asked to contact the investigation team by calling the Police 105 number and quoting file number 201130/9428.
SEXUAL HARM - DO YOU NEED HELP?
If it's an emergency and you feel that you or someone else is at risk, call 111.
If you've ever experienced sexual assault or abuse and need to talk to someone contact Safe to Talk confidentially:
• Call 0800 044 334
• Text 4334
• Email support@safetotalk.nz
• For more info or to web chat visit www.safetotalk.nz
Alternatively contact your local police station -
click here for a list.