"It will take a very long time, we probably looking at an all night stint," Netcare 911 spokesperson Chris Botha told eNCA.
About a 100m of concrete slabs which were about 45cm thick had crashed to the ground.
He said it was a mangled mess under the concrete.
According to eNCA one worker was killed after the roof collapse.
Emergency services said at least 26 people were taken to hospital with “massive traumatic injuries”.
Botha said he hoped that others would be found alive.
The shopping mall was under construction.
"We have an unconfirmed number of 50 people [trapped inside]. It is a shopping mall which was under construction," he said.
Mandy Govender, a police spokesperson, says sniffer dogs are combing the area for survivors.
Ethekwini fire department chief Mark te Water confirmed a
building had collapsed in the area. Workmen were trapped and his department had
dispatched units to the scene, Te Water said.