A faulty lawnmower is thought to be the cause of a house fire that became so big it forced drivers to pull over on a nearby motorway just south of Auckland.

Kamaldeep Sharma had spent the morning and early afternoon yesterday doing a spot of gardening at his home in Pōkeno - cutting back bushes and mowing the lawn.

But shortly after 2.30pm, he spotted flames coming from the backyard and ran out of the house with his 13-year-old daughter Ilina.

"It was still small. I grabbed the hose and I tried to get it out, but it was too windy.

"It was very bad and [became] strong very quickly. The house is destroyed - there's nothing left."

The skeleton of a lawnmower can be seen at the bottom right of this photo. Photo / Supplied

Sharma said he believes his lawnmower, which sometimes became overheated, had caused "a spark" that then lit up dry grass and leaves at the back of the property.

Fire crews received emergency calls from 2.46pm.

The first of the firefighters to arrive got there about 20 minutes after the blaze broke out, he said.

A family friend, who is also a resident on the street, was driving past when she first noticed the flames and realised it was Sharma's house.

She described the ferocity of the fire and could not believe how quickly the flames engulfed first the backyard, the deck and then the whole house.

"I saw the gazebo was on fire and the flames were in the sky.

The aftermath of the house fire in Pōkeno yesterday. Photo / Supplied

Home owner distraught as family home goes up in smoke

"We turned the car around and by the time we came back around, the whole house and the entire roof was on fire."

The woman said it was a sad time for Sharma, who had been distraught at the sight of the family home going up in smoke.

"We can see the house from ours and I'm not wanting to look at it - it's literally a burnt structure. There is nothing there.

"As soon as you enter the gate, it's just the motorway you can see."

The house, on Hillpark Drive, sits near busy State Highway 1.

As the flames became larger, massive plumes of black smoke billowed into the sky and nearby motorway - forcing drivers to pull over for some time.

Sharma said he was now working to figure out what he would do next.

He acknowledged he was being supported by some family and friends and that members of the local Pōkeno community had come forward offering to help the family.