Declaring a national state of emergency is an option when a disaster or other event is or is likely to be of such severity that it is beyond the resources of the local Civil Defence groups.

Six people have today been arrested for theft and burglary in the quake-hit Christchurch CBD.

Police have abandoned all hope of finding survivors at the collapsed Canterbury TV building in central Christchurch, with a police chief saying he was "100 per cent" certain those trapped inside were dead.

Search and rescue teams could continue looking for survivors for a second night following yesterday's Christchurch earthquake, Civil Defence national controller David Coetzee says.

In an emotional reunion, a woman trapped for more than 25 hours in a cramped, dark space in the destroyed PGG building has finally been rescued and reunited with her worried husband.

Rescue personnel have been pulled back from the central city as the 26-storey Hotel Grand Chancellor building is on the verge of collapse.

Christchurch's Rolleston prison will be cleared to create beds for the influx of rescuers into the city.

Hundreds of specialist search and rescue personnel from around the world are arriving in Christchurch.

Rescue services have stopped work at CTV and are now focusing on the Pyne Gould building, where as many as 50 people are thought to still be alive.

Information about what's been damaged in the aftermath of the magnitude 6.3 earthquake and where people can get help.

KEY

Blue markers: Damage to infrastructure and buildings

Red markers: Closures and restricted areas

Yellow markers: Triage centre and welfare centre locations

Green markers: Water supplies and other services for residents

Purple markers: Operational ATMs and petrol stations

Pink markers: Supermarkets and schools that are open

Rescuers have recovered and identified 55 bodies and are yet to identify a further 20 bodies from yesterday's earthquake in Christchurch.

The Government has declared a national state of emergency after yesterday's 6.3 magnitude earthquake in Christchurch.

Christchurch Mayor Bob Parker says emergency cash grants will be made available for victims of yesterday's quake.

Cabinet will hold an emergency meeting at 9.30am to decide whether to declare a national state of emergency, Prime Minister John Key says.

Rescue workers are having to leave bodies in the streets of Christchurch as they focus on trying to save survivors of yesterday's devastating 6.3 magnitude earthquake.

The official death toll from yesterday's earthquake in Christchurch has been revised to 38, but there are fears it could reach as high as 300 as rescuers uncover more bodies in the rubble.

Hundreds of displaced people flocked to the Burnside High School evacuation centre last night to take shelter.

Prime Minister John Key flew into Christchurch to what he says were scenes from a horror movie.

When the shaking begins, my first thought is "it's just another aftershock". There have been plenty in Christchurch since the big quake.