Firefighters are still fighting a blaze at a scrap metal yard in South Auckland, the third fire at the same site in 11 years.

A 12m-high pile of 1600 tonnes of scrap metal, including old car parts, roofing and tyres, is burning at Sims Pacific Metals on James Fletcher Drive in Favona.

The fire was first reported at 1.56am on Wednesday and at its peak the fire had flames "as high as warehouses".

A 12m-high pile of 1600 tonnes of scrap metal, including old cars part, roofing and tyres, is burning at Sims Pacific Metals. (Photo / Brett Phibbs)

It's not the first time there has been a fire at the site, there have been two fires in the past 10 months and three in the past 11 years.

In May 21 last year, 12 fire trucks and two aerial appliances attended a large fire at the site around 12am.

The fire began in a 10-metre by 10-metre area at the top of the three-storey building, where metal was crushed and shredded.

In 2007 there was another blaze at the site, thought to be started by exploding aerosol cans.

Two excavators were currently breaking down sections of the scrap heap at a rate of 20 tonnes an hour and pouring water on the fire throughout Wednesday and overnight, a Fire and Emergency spokesman said.

At its peak over 80 firefighters and 20 fire engines were in attendance.

The blaze was expect to continue burning into Thursday night.

There has been no reported injuries.

Fire crews at the scene of the blaze. (Photo / Brett Phibbs)

The smoke from the fire resulted in the self-evacuation of several businesses in close proximity to the blaze, as well as one of the country's most prestigious private schools.

Students and staff were instructed to head home from King's College around midday today, as dozens of firefighters continued to battle the out-of-control fire nearby.

The nearby Sir Douglas Bader Intermediate School had no plans to close the school on Wednesday or on Thursday, a spokeswoman said.

The fire was covering an area 100m by 70m, and was 12m high in some places, Fire and Emergency New Zealand assistant area commander Auckland City Barry Fox said.

"Before the cars were shredded they were drained of fuels and oils, but there are still some minor explosions going off, in tanks, bits and pieces within the scrapheap."

Auckland Emergency Management were encouraging people living in the area to keep out of the smoke, stay inside and shut all doors and windows and close down ventilation systems if they could.

Any smoke residue should be wet wiped from hard surfaces, especially areas where food is prepared, floors and windowsills.

One witness said the pile of scrap metal was about 12m high and one could "feel the heat from about 100m away".

Another said the flames were "as high as the warehouses around it".

According to the Companies Office Sims Pacific Metals Limited had one New Zealand director, Hamish McBeath, and three Australian directors.

Fletcher Steel owns half of the company.

Thick grey and white smoke can be seen spewing from the fire. (Photo / Brett Phibbs)