KEY POINTS:
Prime Minister John Key has attacked as "totally unacceptable" a failure that sent a huge power cable crashing on to houses.
Up to 20 people were trapped in their homes when the 250m length of cable snapped and fell 7m from the pylons supporting it onto the road
and at least 16 front lawns on Whetstone Rd in Flat Bush, Manukau.
It damaged cars and homes, and burnt through fences.
Some residents fled when they got the chance and ran across the street, but others had to stay indoors as the live wire sent out sparks.
Mr Key last night attacked Transpower, which has been under fire since a power cut last week which left up to 74,000 Auckland homes and businesses without electricity.
"It's totally unacceptable," Mr Key said.
"There is going to be a massive expenditure on the upgrade of Transpower's grid to make sure that that network is not only reliable but safer."
Whetstone Rd residents said an explosive "boom" rang through the street, when the cable - a 220kV conductor line running from Otahuhu to Whakamaru - fell shortly after 10.30am.
Contact with a live wire could have been deadly, but Transpower's general manager of system operations, Kieran Devine, said the line was live when it hit the ground only for "fractions of a second".
"We will do whatever is needed to ensure, to the best of our ability, that this does not happen again."
Cuc Huyuh's kitchen was badly damaged when the fusebox in her garage exploded, burning a hole through the wall into the kitchen.
Speaking through her son-in-law, Tha Lam, she said: "I was in my room when I heard a loud 'boom!' I ran into the kitchen and through the garage and the fuse box exploded - there was smoke everywhere."
The grandmother of two said fearing for her life, she ran outside to see other residents fleeing their homes.
"I was very scared. It was like a mine exploded - so loud," she said.
Jashmin Ali was at home with her three-year-old son Farhaan when she heard the explosion.
"I saw the smoke and the sparks and just grabbed my son and ran. I was so scared - I was shaking as if I come from ice."
Ms Ali and her son had to stay in their house as the live wire sparked outside.
Fire trucks were called to the scene and police closed the road and diverted traffic, while linesmen worked for up to two hours to fix and remove the broken powerline.
Mrs Kumar, who has two sons, said: "This place is just full during the evening.
"Thank goodness it happened when it did. If it was after 3 o'clock, someone would've died."
Mr Devine said it seemed that a joint in the centre of the span of the cable may have failed.
Transpower was still investigating what caused the failure last night.
Mr Devine said this was the first time a major cable had fallen in an urban area.
"We've had about three of these [accidents] throughout the past 12 years - they're rare but they do happen."
One family was relocated last night. Transpower said it would pay for any damage to properties.
