A huge swathe of West Auckland was plunged into darkness due to a reported substation outage this evening.
Vector crews are still assessing what has caused the power outage, which affected at least 17,000 homes as well as street and traffic lights.
New Lynn, Glen Eden, Green Bay, Avondale, Kelston and Henderson are among the affected areas.
Power has now been restored to most homes, with about 200 in New Lynn still in darkness, a Vector spokeswoman said. Most of those homes were near Great North Rd.
The spokeswoman told the Herald a crew was assessing "a few possible causes".
The main cause is thought to be a car hitting a pole on Great North Rd, affecting some significant carrier lines, she said.
Northern fire communications shift manager Colin Underdown said there had been reports of a car hitting a power box in the New Lynn area but there was no sign of that accident.
However some power lines were down near Great North Rd and Brandon Rd in New Lynn, he said.
A police spokeswoman said a loud bang had been reported in the area just before the power cut hit.
However the Joint Traffic Operations Centre had reviewed camera footage in the area but had found no evidence of a crash.
The power outage was first reported just before 10.30pm.
Mt Roskill was also affected by the outage. Pramesh Sundarjee, who lives in May Rd, said power went out at his home around 11pm.
He said there was no flickering - just a sudden "bang" as the electricity died.
He assumed it was only his home but looked out to see all the street lights south of his house had gone dark, though his neighbours on the other side still had electricity.