CHRISTCHURCH, New Zealand (AP) -- 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.