The death toll reached 113 Thursday, with more than 200 still missing. No one has been pulled out alive since Wednesday afternoon.
Police say up to 120 bodies may be entombed in what's left of the Cantebury TV building, which also housed an English language school and offices. Twenty-three bodies have already been pulled from the wreckage.
"It was just horrific," 63-year-old teacher's assistant Kevin Fitzgerald said of Tuesday's quake, which sent him scurrying under a desk along with a student at a school as the building undulated menacingly.
"I thought the devil was coming up out of the earth," he said.
Officials are appealing to families of the missing to be patient. They say they don't want to rush the identifications of the dead and possibly make mistakes.
Crews are also working to secure buildings left unstable by the quake.
The damaged buildings in and around Christchurch numbered in the thousands, including many of the older structures in Lyttelton, a port town just southeast of the city and closer to the quake's epicenter.
School classes in the city were suspended, and residents were advised to stay home as rescue and recovery efforts continued.
The Associates Press contributed to this report.