Power has been restored in Napier after about 20,000 people were affected by an outage just before 11am this morning.
Unison relationship manager Danny Gough said the power was restored gradually to residents after the cut, with about 1600 people the last ones to be put back on just before 12.30pm after the Bluff Hill substation was checked.
He said technicians were now at the Redcliffe Substation analysing data to determine the state of the network, and try and discover the cause of the outage.
"At this stage we are still not quite sure, but hope to know by later today."
He said Unison was keeping customers updated on its website and Facebook page.
