Their hopes were boosted over the weekend when one of the construction workers was found alive after six days without food and water.

Authorities said 24 construction workers who were on the site when the unfinished five-story building came down have been confirmed dead, while another 28 are missing, raising the possibility that the death toll could ultimately be above 50.

More than 600 emergency services and other personnel have been involved in the search for survivors in the wreckage of the building in the city of George on South Africa's south coast, which collapsed last Monday.

There were 81 workers on the site when it collapsed, and 29 have been pulled out alive, the city said. It said 13 of them remained in a hospital without giving details of their condition. The city has previously said that many of the survivors were in critical condition when they were found.

The disaster management team overseeing the emergency response maintained that the operation was still rescue rather than recovery, pointing to the survivor pulled out on Saturday.

The man, who was identified as 32-year-old Gabriel Guambe, was in stable condition in the hospital and “remarkably sustained only minor injuries,” the city said. Guambe was trapped in the rubble for 118 hours, it said.

His survival underlined rescuers' hopes that there may be more people alive in what they called voids in the ruins of the building — areas where there are gaps between the concrete that might have allowed some workers to survive the collapse.

Rescue teams have been using cranes and other heavy machinery to move some of the thousands of tons of concrete in an attempt to reach deeper into the wreckage. Sniffer dogs were also being used and one was responsible for locating Guambe.

Many of the workers were foreign nationals from Mozambique, Zimbabwe and Malawi and authorities were calling for translators to help communicate with survivors. They also said it was making the identification of victims difficult.

Multiple investigations into the cause of the building collapse were underway, including by police, who declared the site a crime scene. The construction company responsible is being investigated to see if it followed proper safety protocols.

People began leaving flowers around the edge of the site as a mark of respect for the victims, while the city and the disaster response team issued a joint statement asking South Africans to observe a moment of silence at 2.09 pm on Monday, the exact time the building collapsed last week.