South Africa ended rescue efforts at the site of a deadly building collapse Friday, having revised down the number of people that were at the premises when the accident happened.

At least 33 people were killed when an under-construction five-storey building came crashing down in the southern town of George on May 6.

Another 29 were pulled alive from the rubble during search and rescue operations lasting 260 hours, the provincial government said.

"This has been an exceptionally difficult time for us all," said Western Cape premier Alan Winde, adding focus would now shift on the investigation.

"My heartfelt condolences go to the families of the 33 victims. We share your pain and will do everything we can to hold those responsible for this tragedy accountable."

Authorities said that, based on information received from the contractor, police had estimated at 81 the number of people, mainly construction workers, thought to be at the site when disaster struck.

As operations ceased, the figure was lowered to 62.

The George municipality said six of the deceased were women and 27 men. Four were yet to be identified, while 10 survivors remained in hospital.

"This operation saw a rescue rate of 54.8 percent, which is truly remarkable," said Winde, comparing it to what he said was a much lower international rate in similar building collapses.

"This is testament to the brave and professional work of our rescue workers."

The building was to house 42 apartments and had received planning permission.

The reasons for the collapse are yet to be established.