A thick black plume of toxic smoke has spread over the eastern and southern parts of Auckland after a scrap metal yard fire in the middle of the night.

The blaze at Sims Metal on James Fletcher Dr in Favona continues to burn, hours later.

Fire and Emergency New Zealand sent out a series of warnings to residents in the affected suburbs alerting them to “close all doors and windows” and encouraging them to not be outside unless necessary.

They also advised people to wear a mask if they were out of their homes.

Firefighters continue to control the blaze at a South Auckland scrap metal yard. Photo / Mike Scott

Fire and Emergency New Zealand district manager Brad Mosby told 1News that composites of plastics mixed with the scrap metal were cause for concern of toxicity.

NIWA principal scientist air quality Guy Coulson told the Science Media Centre that exposure to smoke of any kind was generally “bad” as it can contain all kinds of nasties.

“For example, even wood smoke has a dozen or more known carcinogens in it and hundreds of other organic compounds of undecided or unknown toxicity,” Coulson said.

“There are two main ways smoke causes harm. Particles, any composition, irritate and inflame the lungs causing respiratory symptoms.

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 “They also enter the bloodstream and cause cardiovascular problems – all the way up to heart attacks and strokes.”

Fire at South Auckland scrap yard is sending smoke across the city. Photo / Sean Tracey-Brown

Coulson said on top of that there was toxicity- how poisonous the compounds in the smoke were, gaseous or particulate.

Cars and other vehicles have a complex mixture of plastics, composites and heavy metals, not to mention residual oils, etc.

“All of these will be released into the air in a fire,” Coulson said.

“Burning plastics can release any number of carcinogens, the results of exposure to these may not become apparent for years, and other compounds that are more immediately harmful.

“Without knowing what materials there are, it’s impossible to say much more than general comments.”

Firefighters are battling blaze in a pile of scrap metal at a yard in South Auckland's Favona. Photo / Hayden Woodward

Coulson said anyone immediately in the direction of the wind was at risk.

“Particularly those with respiratory or cardiovascular conditions.

“How much at risk depends on lots of things but chiefly how windy it is and how close they are.

“Looks like there’s a moderately breezy southwesterly at the moment, which will take it over Ōtāhuhu and maybe Howick, maybe Mission Bay and out to sea.”

Wind change spreads smoke

A change in the wind had pushed the toxic smoke across more suburbs in Tāmaki Makaurau as crews continue to battle the blaze.

The blaze stopped trains in their tracks for nearly two hours, toxic alerts were issued to residents earlier in the morning and a dozen fire crews are involved in fighting the fire at Sims Metal on James Fletcher Drive. Limited train services were running.

Fire and Emergency’s Waitemata assistant area commander, Garry Lane, said they responded to the third alarm fire on James Fletcher Drive - triggered by a pile of car parts that had caught fire.

As the morning progressed, smoke billowing from the blaze began making its way across the southern and eastern regions of Auckland - with residents reporting its reach over the last few hours.

Mosby says there has been a shift in the wind and smoke from the fire is now moving north to include suburbs of Greenlane, Ellerslie, Mt Wellington and Penrose. South Auckland remains affected by the smoke.

“We’re asking people to take care and keep their windows and doors shut,” he said, “and wear a mask as a precaution while outside.”

A FENZ spokesperson had earlier said the fire had been contained to the scrap metal pile but it would be burning for some time.

“The smoke plume is significant and is likely to remain that way throughout the day.

“There are concerns the smoke from the fire is toxic and may affect people in the area. Auckland City Council environmental and pollution officers are also in attendance at the fire.”

FENZ said on arrival firefighters found a 70 by 70 metres,10 metres high pile of scrap metal on fire.

“Up to 30 trucks and support vehicles have attended the incident throughout this morning.”