President Cyril Ramaphosa offered his condolences to the families of the deceased and called for an investigation.

"Investigations into the cause of the incident must aim to bring closure to the community and prevent a repeat of this disaster," Ramaphosa's office said in a statement, Reuters reported.

Twenty-six construction workers who were at the site of the unfinished building when it collapsed have been removed from the rubble, while 49 remained unaccounted for, the municipality of George, a coastal city east of Cape Town, said in a statement.

"Three teams of rescue personnel are currently working on three different areas within the site of the collapsed building," it said.

A drone view of the site showed rescue workers removing debris in a bid to reach those still under the rubble.

"We are focusing on the areas... where we have actually been hearing people," Colin Deiner, chief of disaster management for the Western Cape province, told reporters at the scene.

CCTV footage obtained by Reuters showed a cloud of dust as the building crumbled on Monday afternoon.