One person remains in a critical condition at Christchurch Hospital after a gas explosion at a house yesterday morning.
Three people are in stable conditions at Christchurch Hospital, while another person might be transferred to the serious burns unit at Middlemore Hospital, a Christchurch Hospital spokesperson told 1 NEWS.
Another person has been discharged this morning.
One house, on Marble Court in Northwood, was destroyed in the explosion, five were "severely affected" and 17 others were impacted by debris, Fire and Emergency New Zealand.
Police said in a statement today they are still at the scene while an examination is carried out today and tomorrow by police, Fire and Emergency NZ and WorkSafe investigators.
Twelve properties in Marble Court remain unsafe and residents of those properties are unable to access their homes, the statement says. Cordons remain in place.
Insurance company Vero told 1 NEWS they had customers in eight affected houses, ranging from "minor" damage to "more substantial" - including ceilings blown in and double-glazing windows gone.
Vero will be visiting houses today.
Witness at the scene Ann Gray told 1 NEWS yesterday her house shook and she originally thought the explosion was an earthquake, she would have guessed about 7.5 magnitude.
But then saw debris, including wood, billow into the air.
"It was massive ... bits of wood and everything," she said. "It was like the whole house had exploded."
Brad and Megan Culver, who live directly behind the house which exploded, also recounted the moments they pulled injured people from the ruins.
"The house [which exploded] was in a complete pile of timber, and rubbish. You couldn't even conceive that it was a house, there was nothing left standing," Mr Culver said.
A gas expert said he has never seen such a serious gas explosion during his 25-year career.
"Those pictures from the site today were horrendous and I feel sorry for the occupants and obviously it's a hugely devastating event that they went through," Master Plumbers director Martin de Gouw said.