"The power is currently off at the Te Marua water treatment plant and we're expecting to have electricity restored at midnight.''
He said the incident would not affect the water supply for the area.
Police and the regional council would investigate the incident.
"We're an organisation that takes workplace health and safety extremely seriously, so we'll be looking at this to find out what happened and to make sure we've got processes in place to stop it happening again,'' Mr Sangster said.