About 10 vehicles were destroyed and dozens of nearby households and shops were forced to evacuate following the collapse of a top section of a high-rise apartment building that had been under construction in the city's Hwajeongdong district.
The incident on Tuesday afternoon left piles of debris spilling across nearby streets.
Emergency workers rescued three labourers, including two who had been trapped in a shipping container pounded by rubble, but their operations were halted hours later over concerns that the 39-floor structure could further cave in.
Following a safety inspection involving government and private experts and camera-equipped drones that flew around the building's crumbled exterior, which is now exposing mangled steel beams, emergency workers were seen re-entering the site with search dogs on Wednesday afternoon.
Gwangju Mayor Lee Yong-seop said the inspectors concluded it was safe enough for rescuers to enter the inside floors of the building. However, inspectors were concerned about areas near the structure's crumbled exterior, which Mr Lee said would be predominantly searched by drones and dogs.
Officials said 394 workers had been employed at the construction site, including the six who remain out of contact following the accident.
Lee and other officials did not specifically mention the possibility of the workers being found alive.
The city government has suspended all ongoing construction work in Gwangju by HDC Hyundai Development, the main contractor of the apartment project in Hwajeongdong, as it opened an investigation into the cause of the accident.
Gwangju was the site of a fatal accident in June last year, when a five-storey building that was being demolished collapsed and sent debris falling on to a bus, killing nine people on board.
South Korean President Moon Jae-in ordered officials to investigate the cause of Tuesday's collapse and called for stronger safety measures to prevent similar accidents, his office said.
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