Efforts are ongoing in South Africa to locate approximately 50 individuals who disappeared following the collapse of a five-story apartment building on Monday.

Since the incident occurred in the coastal city of George, at least six fatalities have been confirmed.

Rescuers made contact with 11 additional survivors amidst the wreckage of the building under construction on Tuesday.

Among them are four individuals trapped in the basement. Authorities are investigating the cause of the collapse.

At the site on Tuesday, emergency responders took turns working on the small area, manually removing concrete blocks and debris.

Periodically, the team leader raised his fist, signaling for silence. Everyone halted, hopeful that someone had been found. Some instances turned out to be false alarms, and the noise resumed.

The majority of the workers believed to be on the construction site, estimated to be at least 75 individuals, remain unaccounted for. Bringing survivors to safety has been a slow and challenging process.

"They will then begin a process of lifting the different floors off each other," said Colin Deiner, chief director for disaster management.

"There is a possibility people could still be alive," he added.

The entire rescue operation is expected to take between four and five days.

Video footage taken nearby showed a huge cloud of dust as the building fell.

The site has been cordoned off from the public. But there were still many people standing around the perimeter in shock and disbelief.

South African President Cyril Ramaphosa said his thoughts were with the families of people who died in the incident and called for the investigation to "bring closure to the community and prevent a repeat of this disaster".

The city's mayor, Ald Van Wyk, sent his condolences to the families "and all those affected who continue to wait for word of their loved ones".

Overnight, more than 100 rescuers with sniffer dogs worked to locate those trapped in the building. Heavy lifting equipment was used to assist the operation.

Photos of the area now show a completely flattened construction site, with parts of the building's roof lying atop the rubble.

"I saw one guy was working and then 'boom' and I saw the whole building collapsed... I'm also traumatised. It is very sad," local councillor Theresa Jeyi said.