Planners estimate that the central business district will be unusable for months.
Officials say at least 145 people are confirmed dead after Tuesday's 6.3 quake, with about 200 people from more than 20 countries still missing among the ruins.
Fresh aftershocks have sent masonry tumbling among rescuers.
The New Zealand authorities admit they expected the toll "to steadily rise" over the weekend.
Families were warned to prepare for the "worst type of news" after another day drew to an end with no sign of life beneath the rubble.
So far only six quake victims have been formally named,but police were continuing their attempts to identity the deceased. Read More