More than 100 people may have died in Christchurch's quake-ravaged Canterbury TV building, which police say was "unsurvivable".
The confirmed death toll from Tuesday's devastating magnitude 6.3 quake stands at 75, with 300 reported missing.
But police expect the death toll to climb and it will do so appreciably if the estimates about those missing in the CTV building are correct.
Fifteen CTV staff and a number of Japanese students from a foreign language school that operated in the building are believed to be among those in the rubble.
Canterbury police district commander Superintendent Dave Cliff gave the estimates of between 80 and more than 100 for those missing in the CTV building, soon after a colleague said that rescue work at the site had been halted by safety concerns.
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Inspector Dave Lawry said he was "100 per cent sure" there were no survivors in the building.
Hope is also fading for those trapped in the Pyne Gould Corporation building in Cambridge Terrace, though at least four people were pulled from the debris there on Wednesday, the last a woman - who had been trapped for 26 hours - around 2.30pm local time.
There had been no communication with anyone trapped in the building for some hours since then.
"We are reaching that phase where hope is beginning to fade, but we are still there," Cliff said about the PGC building.
On Wednesday night Pyne Gould Corporation chairman Bruce Irvine confirmed 14 people remained trapped in the building.
Twenty two people are believed by police to have died in the collapse of Christ Church Cathedral. Police dogs had been through the area of the 130-year-old city landmark and officers were confident there were no survivors there, Cliff said.
One of the city's tallest buildings the Grand Chancellor Hotel in Cashel Street is teetering.
Reports said the hotel had slumped in one corner, prompting fears that should it collapse it could destroy surrounding buildings.
It has been a grim time in the central city, with medical staff in rescue teams having to amputate limbs to help free people trapped in rubble.
Cliff said despite the lack of contact with people in the collapsed buildings, police were remaining optimistic.
"It is certainly possible that people could be in cavities in some of those sites, so we are not losing hope. The urban search and rescue teams are here for that purpose."
