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Power has been restored to Rotorua after an "explosion" at a Transpower sub-station cut electricity to the city for around an hour.

The blackout brought the CBD to a standstill, with many shops having to close their doors.

Unison Network spokesman Bill Hewitt said the power cut affected around 12,000 people.

"We had a problem at the Transpower substation - there was an explosion," he said.

- NEWSTALK ZB / HERALD ONLINE STAFF