Energy Safety - part of the Ministry of Economic Development - has launched a preliminary investigation into the damage to a high-voltage power cable in Dunedin last week.
The authority, which oversees compliance with energy laws and safety, was conducting the initial inquiry to determine whether a full investigation was required, Energy Safety operations manager Mark Wogan said yesterday.
He planned to speak to the parties involved over the next few weeks, before deciding if more action should be taken.
"We have requested information from different people who are involved, trying to find out what's happened.
"Until we get that basic information, we are certainly not going to jump to any assumptions or conclusions," Mr Wogan said.
The move comes after one of Dunedin mayoral candidate Lee Vandervis' volunteers pierced an 11,000-volt power cable while hammering a steel peg into a designated election advertising sign site in Quarry Rd, Mosgiel.
He was not injured.
The power cable failed later, after moisture entered through the damaged section, cutting power to 747 customers from East Taieri to Taieri Mouth for about 40 minutes.
Neither Dunedin City Council staff nor election candidates were aware cables ran under the site, but council staff have since warned more cables - as well as reticulated gas and other services - were under some election advertising sites in the city.
On Friday, council resource consents manager Alan Worthington said he was confident the cables had been installed "in accordance with their requirements".
The network is owned by Aurora Energy Ltd and managed by Delta Utilities Services, both council-owned companies.
The cables were said to be buried 600mm down.
The Quarry Rd site lacks buried power cable warning signs.
Mr Wogan said existing New Zealand legislation mentioned only the general requirement for safe practices when installing and maintaining services, but did not include specific rules for the depth cables were buried.
"There are no specific requirements for the depths of works in this situation," he said.
International codes were more detailed, with Australian standards stipulating minimum installation depths of 750mm for protected high-voltage cables and 900mm for unprotected ones, plus an appropriate way to identify cables routes from above ground.
However, there was no requirement for international guidelines to be followed in New Zealand, Mr Wogan said.
