Investigators are still struggling to identify the cause of an explosion that destroyed a Christchurch house.

Several items of interest have been found at the blast site.

Fire and Emergency New Zealand (Fenz) is continuing to investigate the cause and origin of the gas explosion that obliterated a Marble Court house in the northern suburb of Northwood on July 19.

READ MORE: Christchurch gas explosion: 'Distraught' contractor who worked on house gives families condolences

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Blast waves threw chunks of roof tiles and other debris around the neighbourhood.

One Greymouth man was rushed to Christchurch Hospital where he was placed on life support.

Five others were also taken to hospital.

Neighbours and passers-by who pulled stunned survivors from the burning debris told the Herald at the time they were amazed that nobody was instantly killed.

Over the past week representatives of Fenz, WorkSafe, police and the insurance industry have worked together to reconstruct large portions of the house in which the blast occurred to gain a clearer picture of what happened.

But the cause of the blast has not yet been definitively established.

Fenz Christchurch Metro Area Commander David Stackhouse indicated that the investigation will likely continue over the coming weeks and will include the testing of several items of interest found at the blast site.

Personal belongings, including photo albums, have been recovered from a number of the properties badly affected by the explosion and returned to their owners.

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"For many families photographs are their most important belongings," Stackhouse said.

"Those working on the investigation were delighted that they were able to reunite many of the people affected by the explosion with these irreplaceable items."

The scene of the incident remains under guard while the investigation continues.

* If you have concerns about your gas system, contact your gas retailer or a licensed gas worker to check the installation. If you notice a gas smell that persists after you turn off your gas appliances or supply, get outside to a safe place and call 111. For more information and tips about gas safety visit www.gassafety.org.nz.