Wellington power station fire out

Fire crews stand-by after the explosion. Photo / NZPA

An electrical fault caused an explosion and fire at the Haywards Power Substation in the Hutt Valley today, Transpower said.

Nobody was injured as a result of the fault, which occurred at 11.40am, chief executive Patrick Strange said.

Power was cut to parts of Wellington for about one second as the supply was immediately rerouted.

Mr Strange said the site was evacuated as a precautionary measure.

Transpower communications manager Rebecca Wilson said a piece of equipment in the basement of a large building was being "put back into service" and caused the explosion after being switched on remotely.

When emergency services arrived there were five or six people unaccounted for, but they were soon located working off-site, Stu Cleland, Hutt City Fire Senior Station Officer, said.

Fire fighters were unable to enter the building until 2.15pm, once the black smoke had been cleared and building isolated from the main power supply.

"Turned out it was a small fire, but because of the high voltage cabling we couldn't go in there," Mr Cleland said.

"We couldn't put the firefighters at risk."

The fire had been contained by sprinklers and took about 15 minutes to put out, he said.

An explosion at the substation in 2003 killed 22-year-old Kurt Stott and left his colleague Andries Nieman with serious burns.

- NZPA