A gas explosion triggered by a light switch is believed to have caused a West Auckland house fire this morning.

The walls of a house at 59 Mary Dreaver St, New Windsor, were flung several metres by the blast, causing the roof to cave in and injuring two people inside.

A 42-year-old woman was taken to Middlemore Hospital with serious burn injuries and a man with moderate injuries was taken to Auckland Hospital.

Footage obtained by Focus showed the charred remains, and the walls of the house blown against the back of another house in front.

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The family living at that property declined to be interviewed, but appeared shaken, the kids all dressed in their pajamas, as they got into a car and drove off.

Avondale senior station officer Chris Power said it appeared it was a gas explosion, possibly due to a leak.

He said the two people inside the house reported smelling gas at about 4am.

"And at approximately six o'clock this morning, one of the occupants got up and turned on a light and it appears that was the source of the ignition, which caused the explosion."

Power said investigators were at the scene and are yet to confirm the cause.

Several residents on the street said they all heard the powerful explosion and didn't know the pair who resided at the house.

Darshana Dabhoya lives across the road at number 56.

"We were just sleeping and I heard a big blast. I could hear a lady screaming really bad... really scared. And I could also see the flames and smoke coming from the house."

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Priti Patel, who runs the Alpine Superette nearby and lives above it, said she heard "a big bang" and saw big flames from her window.