An Auckland family have been left petrified at how quickly a neighbouring house became engulfed in flames.

Sanjaya Hewamanage was in his bedroom of his Church Rd, Mangere Bridge home, when he spied what looked like flames out his window just before 10pm last night.

By the time it took him to walk out his front door a house across the road was fully enveloped in fire.

"I saw some sort of flames from my window and thought 'oh he's got a fire going'. When I came out of my house the whole house had caught fire.

"It was so fast, I can't imagine how anyone could escape. I have never seen that kind of fire before. It was only a few seconds."

The sole occupant of the house was later found, Fire and Emergency confirmed at the scene.

"Firefighters noticed the victim in the front room of the house as they got to work," the senior officer said.

Although the cause was still being investigated, he said it was a timely reminder for people to be aware of the 'metre from the heater' rule - keeping combustible materials at least one metre away from heaters, whether they were electric, gas or an open fire.

Seven fire appliances and three ambulances eventually made it to the scene.

Hewamanage said soon after the flames took hold the windows of the home began exploding, with glass spewing on to the nearby surrounds.

"It was very scary."

He said after the fire his wife immediately went round the house turning off all the heaters as they thought that might have been the cause.

"We now see an old burnt out house now. It's very sad."

Another witness told the Herald she was on her way home at 9.52pm when she glanced out only to see "flames shooting out of the side window".

"The fire was vicious and you could hear explosions as parts of the house caved in and collapsed," Eve Schell told the Herald on Sunday.

Auckland fire risk management officer Robert Watson said the home was "extensively damaged".

"There's not a room in the house that hasn't sustained some form of damage."

The fire started toward the front area of the house, he confirmed.

"It's not suspicious. We're dealing with a sudden death which is why police are also involved."

A police spokesperson said a scene guard was placed at the property overnight.

A scene examination was taking place today.

"We are working with fire investigators at the scene to determine the cause of the fire.

"A post-mortem is expected to take place either today or tomorrow. We are not in a position to release information about the deceased at this time."