The quake has so far caused nearly 100 deaths, with 226 more people listed as missing .
Rescue teams are continuing their efforts to search for quake survivors, but hopes for success are fading.
Power has been restored to much of the city, but many people remain without water.
Police are just starting to release the names of quake victims.
New Zealand rescuers refused to give up the hunt for quake survivors Thursday, despite hope fading for hundreds feared trapped two days after a disaster that has killed nearly 100.
Emergency officials gave the grim news that they could find no signs of life in the wreckage of office towers, churches and homes after the 6.3-magnitude tremor laid waste to central Christchurch and some of its suburbs.
"All over the world when we see disasters like this, we see miracle stories of people being pulled out, days and in some cases weeks after the event," Prime Minister John Key told TV3.
"That does not mean that there can't and won't be people trapped in buildings," he said. "We can't give up hope, but we also need to be realistic."
Police said 98 bodies had been retrieved from the rubble and 226 people were listed as missing. "We're gravely concerned about those individuals," district commander Dave Cliff told reporters.
Rescuers ruled out anyone being found alive at the collapsed CTV building, which housed a TV station and a busy language school for foreign students, and where as many as 120 people may have perished.
They also abandoned hope of finding survivors at Christchurch's landmark cathedral, which lost its spire and where up to 22 people could be buried.
Police released the first names of quake victims, listing four people including two babies aged five months and nine months.
But police insisted hundreds of search specialists including foreign teams, with sniffer dogs, purpose-built cameras and listening devices, were still focused on finding survivors, 24 hours after last pulling anyone out alive.
"If people are alive and trapped we're doing everything humanly possible, with a huge range of people from right around the world," Cliff said.
He also issued a sharp warning to criminals after about a dozen cases of post-quake looting in Christchurch, saying police patrols would "saturate" the city and its suburbs, and strictly enforce a curfew in the center.
Hundreds crowded Christchurch's airport, desperate for a flight out of the city of 390,000.
Up to 30 quake survivors were rescued on the first night but only a handful emerged from the wreckage on Wednesday.
Speaking to the Seven Network on her mobile phone, Anne Vos had gripped millions of TV viewers with her account of being trapped in the mangled Pyne Gould office building before she was rescued late Wednesday.
"I'm hoping they are going to get me out soon because I have been here for so long and it's dark and horrible," Vos, who was recovering in hospital Thursday, had said.
Police Minister Judith Collins said she had seen one corpse retrieved from the Pyne Gould building on Thursday.
"It was just a scene of utter devastation, I've never seen anything like it," Collins said of the wrecked central business district. "If you saw it on a movie screen you would have thought somebody was just making it up, it was so bad."
Japanese search-and-rescue experts were on the scene and combing the CTV site in the shadow of the listing, 26-story Grand Chancellor Hotel, Christchurch's tallest building, which was at risk of collapse.
"This is not just New Zealand's tragedy, it is an international tragedy that is touching the lives of thousands around the world," New Zealand Foreign Minister Murray McCully said.
Power has been restored to much of the city, but many people remain without water. Thousands of residents, rattled by numerous tremors in recent months, have been staying with friends and relatives elsewhere.
Christchurch was hit by a 7.0-magnitude earthquake in September, which damaged 100,000 buildings but miraculously caused no deaths. New Zealand has not suffered such a disaster since 256 people died in a 1931 quake.