Yesterday's quake - the death toll for which stands at 75 - may prove to be NZ's worst natural disaster.

Police say more than 100 people may have been lost in Christchurch's quake-ravaged Canterbury TV building, which they say is "unsurvivable". The official toll from yesterday's devastating quake stands at 75.

Fifteen CTV staff are believed to have died when their central Christchurch building collapsed after yesterday's magnitude 6.3 quake, CTV chairman Nick Smith says.

At least 14 people are missing from two companies in the Pyne Gould building in Christchurch tonight.

A woman trapped in rubble left a harrowing message for her son, in which she said she didn't think she would survive.

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.

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.

Fletcher Construction says its residential repair programme in Canterbury as agent for the Earthquake Commission (EQC) is temporarily on hold.

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.

A man who has more than a dozen close friends and colleagues missing in earthquake-devastated central Christchurch says all he can do is wait and hope they are still alive.

Track the aftershocks rattling Christchurch in the wake of the shallow magnitude 6.3 earthquake.

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

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.

Between the giant rubble littering the rain-drenched Colombo St, police pull another dead body and lay it down on a black tarpaulin.

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