Rescue services have stopped work at CTV because they say they've received no signs of life in eight hours.

Herald reporter Catherine Masters, who has been outside CTV, says the rescue effort is now focusing on buildings where people are known to be alive, such as the Pyne Gould building, where rescuers believe as many as 50 people might have survived yesterday's quake.

The Fire Service said reports of 15 people being pulled alive from the devastated CTV building in Christchurch were based on out of date information.

A spokeswoman for the organisation said all rescue operations at the collapsed and burning central city building have been suspended and handed over to police.

There had been no signs of life for hours and it was unlikely there would be more survivors, she said.

A Christchurch Police spokesman acknowledged operations had been suspended at the site, but said emergency services were waiting for heavy machinery to arrive.

Earlier reports had suggested 15 people have been rescued after more than 20 hours amid fire and devastation in the Canterbury TV building.

Police said they had recovered 75 bodies after the quake - 20 of which had not yet been identified - and Prime Minister John Key declared a national state of emergency.

Pyne Guinness Gould rescues

Transalpine Area Commander Ross Ditmer confirmed one person had been pulled from the collapsed Pyne Guinness Gould (PGG) building in the last hour.

TVNZ reported a woman had been rescued came more than 21 hours after the earthquake and minutes after a man was pulled out of the building.

He had been spotted by rescuers perched on the twisted debris through a gap in the rubble, the broadcaster said.

He had been lifted out, lowered to street level, and taken to hospital, it reported.

Grant Lord, the officer in charge of the rescue site at the PGG building, confirmed workers pulled out three survivors this morning - two women and one man.

Woman trapped

They were also trying to gain access to a woman who was trapped inside the pancaked building but who had been talking to urban search and rescue officers, he said.

Mr Lord said the team was trying to access her from underneath where she is, but if that didn't work they would have to go through the top of the building.

He said the woman did not appear to be injured and was actually "very chirpy" and in good health. The woman had taken cover under a chair or a desk when the earthquake had struck.

Her husband was on site waiting for her to come out and rescue workers with a ladder were going straight into the corner of the building in an effort to reach the woman.

Mr Lord said that the rescue workers had not had communication with anyone else in the building.

He said aftershocks had moved the partially collapsed tower overnight and that the rescue work was extremely dangerous. He did not know how many people were in the building but the team was concentrating its efforts on those who were still alive.

Mr Ditmer said he was hopeful more people would be found alive in the coming hours as USR teams from New South Wales, Queensland and Japan were deployed in the Christchurch CBD.

Superintendent Dave Cliff this morning said there were 55 bodies in a temporary morgue and 20 more were being taken there.

Christchurch Mayor Bob Parker said 300 people were also listed as missing.

"With those 300 missing people could just be someone called up saying so and so is missing - they may have just left town."

Announcing a national state of emergency had been declared, Prime Minister John Key said the whole country was grieving.

Mr Key said the lives lost were the "greatest loss".

"Buildings are just buildings, roads are just roads, but lives are irreplaceable."

He said the whole of New Zealand was with Canterbury.

"Today all New Zealand grieves for you Christchurch," he said.

But he said the city would recover.

"Though lost lives will never be replaced, and though your city will never look the same again, you will rebuild your city, you will rebuild your lives, you will overcome."

Mr Key said he was "very nervous" about speculating about the eventual death toll but with 75 dead and hundreds missing it was likely to rise.

- With NZPA

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