A Transpower fault at Kaikohe saw power cut to 31,000 customers across the Far North this morning.
Transpower NZ corporate communications manager Deborah Gray said the cause of the outage which was reported at 8.46am was yet to be identified.
Gray said there was work being on one circuit which was shut down but a second circuit had tripped causing the mass outage.
Steps were being followed to ensure staff and members of the public were safe and a risk assessment was carried out followed by an inspection before power would be restored.
The outage affected Top Energy customers from about Towai north to Kaitaia.