The number of Christchurch properties without power has been reduced to nearly 6000 on Thursday, but fresh damage to a major cable has created new problems.
Orion chief executive Roger Sutton told a Civil Defence media briefing that a contractor had hit a cable, threatening the power supply to customers in the southern area of the earthquake-damaged city.
Mr Sutton says the damaged cable is leaking oil but is still carrying electricity and is causing no power cuts at present.
The cable will be checked on Thursday night and the lines company expects to know the extent of the damage by Friday.
People in the southern suburbs have been asked to conserve power, just as those in the east are already doing.
Across the rest of the city there are only 1500 customers in suburban areas without power and just over 4000 in the central business district.