Fresh aftershocks sent masonry tumbling among rescuers in New Zealand's quake zone and a cat sparked false alarms Saturday of a possible survivor, as the disaster's death toll rose to 145 with more than 200 missing.

Grim assessments emerged for the fate of the central business district in devastated Christchurch, with engineers and planners saying it will be unusable for months and that about a third of the buildings must be destroyed and rebuilt.

On the outer edge of the district, Brent Smith watched in tears as workers demolished his 1850s-era house, where he had run a bed and breakfast and where antique jugs and a $6,000 Victorian bed were reduced to shards and firewood. His three daughters hugged him, also weeping.

"You don't know whether to laugh or cry but I've been doing more of the latter," Smith said.

Prime Minister John Key, who spent some of the afternoon speaking to families who lost loved ones in the disaster, called on all New Zealanders to hold two minutes of silence next Tuesday to remember victims and the ordeal of the survivors.

"This may be New Zealand's single-most tragic event," Key said.

Key said the government would announce an aid package Monday for an estimated 50,000 people who will be out of work for months due to the closure of downtown.

Christchurch Mayor Bob Parker assured relatives of the missing — including people from several countries who have converged on this southern New Zealand city of 350,000_ that every effort was being made to locate any remaining survivors of Tuesday's 6.3-magnitude quake.

No one was found alive overnight as a multinational team of more than 600 rescuers continued scouring the city's central business district, although a paramedic reported hearing voices in one destroyed building early Saturday, Police Superintendent Russel Gibson said.

"We mobilized a significant number of people and sent a dog in again — and a cat jumped out," Gibson said, adding that a rescue team removed "a significant amount of rubble to be 100 percent" certain that no person was trapped inside.

Police have said up to 120 bodies may be entombed in the ruins of the downtown CTV building alone, where dozens of foreign students from an international school were believed trapped.

Still, Gibson said rescuers weren't completely ruling out good news.

"I talked to experts who say we've worked on buildings like this overseas and we get miracles. New Zealand deserves a few miracles," he said.

The King's Education language school released a list of missing people presumed in the building: nine teachers and 51 students — 26 Japanese, 14 Chinese, six Filipinos, three Thais, one South Korean and one Czech. An additional 20 students were listed with "status unknown."

The death toll rose Saturday to 145 after additional bodies were pulled from wrecked buildings, Police Superintendent David Cliff said. More than 200 people remain missing, he said.

At Christchurch's iconic cathedral, workers had just begun work on its ruined bell tower late Friday when fresh aftershocks sent more masonry tumbling from the building.

Rescuers were immediately withdrawn while the safety of the 130-year old church was reassessed and a new plan made to reach as many as 22 people who may be entombed inside.

The city's central business district will take several months to recover, Earthquake Recovery Minister Gerry Brownlee said, adding that "most of the services, in fact all of the services that are offered in the CBD will need to relocate elsewhere."

Damaged buildings will need to be bulldozed and rebuilt "so that people can have confidence about coming back into the area to transact any business that's here."

One in three of the central city's mostly brick buildings were severely damaged in the quake and must be demolished, earthquake engineer Jason Ingham said.