Residents of the quiet Christchurch street where yesterday's giant gas explosion destroyed a house and hospitalised six people have returned today under police escort to survey the carnage.

A gas contractor who worked on the Marble Court property in Northwood just one day before it exploded arrived at the chaotic scene yesterday and fronted to police officers.

The gas worker voluntarily made himself known to first responders and suggested that police or fire investigators might want to talk to him.

He was devastated by what happened, sources have told the Herald.

Advertisement

It's believed the residents of the Northwood home were having trouble with their gas fire.

The blast at 10.14am yesterday destroyed the house and flung debris across the neighbourhood.

Emergency services and witnesses at the scene said it was lucky no one was killed.

This morning, one person was in a critical condition and three people were in a stable condition in Christchurch Hospital. Another patient had been taken to Middlemore Hospital, where there is a serious burns unit, and another had been discharged.

Canterbury Metro Area Commander Superintendent Lane Todd said police, Fire and Emergency New Zealand, and WorkSafe would be examining the scene today and tomorrow.

Todd said 12 evacuated properties were still unsafe and residents could not return home this weekend. Cordons and security remain in place, while Northwood residents have been asked to turn their gas systems off. Electricity has also been shut off in the area.

Early this afternoon, several Marble Court residents showed up at the police-manned cordon, wanting to check how their properties coped in the explosion, which caused a blast so big it registered as a magnitude-2 earthquake.

Emergency services continue their investigation into the Christchurch gas explosion today. Photo / Kurt Bayer
Emergency services continue their investigation into the Christchurch gas explosion today. Photo / Kurt Bayer

They hugged each other, bought each other coffee, and shook their heads in amazement.

Advertisement

"We're all alright and that's all that matters," said Kay Hobson who, with husband Barry, lives two doors down from the main blast site.

The Hobsons wanted to grab some key items from home today, including Barry's medication.

Indraj and Akita Fonsaka, who live across the road, and whose house was badly damaged, also wanted to get home.

They were waiting for police and fire officials to escort them in.

The Fonsakas had fled with only the clothes on their backs.

Friends and family are looking after them as they said their insurance refused to stump up for temporary accommodation.

Akita and Indraj Fonsaka who live across the street from the Marble Court, Christchurch house that suffered a gas explosion returned to survey the damage today. Photo / Kurt Bayer
Akita and Indraj Fonsaka who live across the street from the Marble Court, Christchurch house that suffered a gas explosion returned to survey the damage today. Photo / Kurt Bayer

Their lives have been thrown into turmoil and they are unsure when they'll be allowed home.

"We were living very peacefully here," Akita said.

"We have lovely neighbours, it's just a nice quiet street."

Today, Marble Court is still littered with debris from the detritus of the detonation. Roof tiles, broken glass, insulation, and other debris remains scattered across the cul-de-sac.

Several houses have suffered major damage, including blasted walls, caved-in garage doors, smashed windows and eaves.

A mobile police command unit is parked down the street, along with a fire truck and other specialist response vehicles.

Fire and Emergency area commander Dave Stackhouse said yesterday all of Northwood was connected to piped gas, but at this stage it was not clear how there had been a leak.

"We've got our gas experts having a look at that," he said.

"Once we've got the scene safe, we'll look at what's caused this and carry out an investigation with police and WorkSafe."

Stackhouse said it was "probably lucky" the house inhabitants were close to the source of explosion when it happened.

"Often with these types of things it's the blast wave that can actually kill people further away from the actual radius of the initial explosion," he said.

"So I guess we are lucky that we are not looking at multiple fatalities here."

Neighbour Bradley Culver was having a cup of coffee and watching the Open Championship golf on TV with his wife when the explosion happened.

The former police officer ran outside and saw a neighbour's house destroyed.

He came to the trapped survivors' rescue.

They were stunned, he said, hardly able to talk.

"I am surprised nobody died [instantly]," Culver said.

"As a former police officer I've seen a lot in my days, but I've never seen anything like that."