Power is out in the Auckland suburb of Hillsborough after locals reported hearing a loud bang.
Electricity company Vector says power may be out for some time as it investigates the cause.
"Vector is responding to an outage affecting customers near the corner of Mt Albert and St Andrews roads in Hillsborough," a spokeswoman said.
"Vector's electricity operations centre has remotely redirected power flows to as many affected customers as possible, and our crews are currently on site investigating. At this stage, it is believed that the cause may be a possible feeder fault."