The official death toll of 75 looks certain to rise considerably as relatives waiting for news of their loved ones following the Christchurch earthquake have been told that up to 100 people have died in a single building.
New Zealand authorities called off rescue operations at the Canterbury Television building after police said they were "100pc certain" no one left inside could have survived.
In a blow to families and friends who were holding vigil for their relatives trapped inside the CTV building in the city centre, police said that reports from early in the day that 15 people had survived and found an air pocket inside the rubble were false.
Lizzie Manning, 18, and her brother Kent, 15, were waiting for news of their mother, Donna, a television producer who worked in the building.
"I'm going to stay here until I know whether she is in there or not," she said.
"She would have been on her lunch break, but she didn't come home last night.
"My mum is superwoman, she would make it home for us if she could, that is what's worrying me.
"She would have dragged herself over there if she could."
Later, a policeman came to deliver the news that no one was left alive inside the remains of the building.
The siblings held each other, kneeling on the wet grass, and cried.
Police said the building collapse was not survivable because of smoke and diverted rescuers from the smoldering wreckage, which also housed an English language school. There was also "no sign of life" from beneath the rubble at the Cathedral, officers said.
There are still 300 poeple unnacounted for following Tuesday's 6.3 magnitude quake.
An Irishman and a Briton are among those known to have died the earthquake, according to Ireland's Department of Foreign Affairs.
The Irishman, Eoin McKenna, was originally from the border county of Monaghan and had a young family. The Briton is married to an Irishwoman, the department added. Both men had been living in Christchurch.
John Key, the prime minister, said it was "a time of great agony" for New Zealand.
Most of the city remained eerily quiet, but in Latimer Square several people found it hard to tear themselves away from the Canterbury TV building.
Elsewhere in the city, chaos reigned. One of the tallest buildings in Christchurch, the Grand Chancellor Hotel, threatened to fall after part of its foundations slipped into a hole in the ground created by the earthquake.
As aftershocks continued to rumble across Christchurch, police cleared two blocks around the hotel amid fears that it would take several other buildings with it when it finally crumbled. Across the city, cold rain fell over whole blocks that lay in ruins.
Roads rippled like carpet and black sludge rose up from underneath buildings and cracked pavements. Police implemented a curfew in the city at 6.30pm after six people were arrested for looting.
Mr Key said the lives lost were the "greatest loss".
"Buildings are just buildings, roads are just roads, but lives are irreplaceable."
In a televised address, he told Christchurch citizens: "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."
Since last September's earthquake, the residents of Christchurch have become used to the grim reality of living in a city pummelled by powerful aftershocks on a near weekly basis. But nothing could have prepared them for the destruction wrought by yesterday's quake.
DAZED, screaming and crying residents wandered the streets as sirens and car alarms blared. With ambulance services overwhelmed, some victims were carried to private vehicles in makeshift stretchers fashioned from rugs or bits of debris.