A total of six bodies, including two children, have been found in the rubble of a collapsed condo building in the Miami-area town of Surfside.

Rescue workers continue to search for survivors in the collapsed building of the Champlain Towers South, on June 30, 2021, in Surfside, Florida.
Rescue workers continue to search for survivors in the collapsed building of the Champlain Towers South, on June 30, 2021, in Surfside, Florida. (AP)

Six more bodies have been discovered in the rubble of a collapsed apartment building in Florida, authorities said, as the search for more than 140 people unaccounted for entered its seventh day.

The official death toll now stands at 18 after most of a building in the Miami-area town of Surfside suddenly pancaked early last Thursday, but hopes are dwindling that the hundreds of rescuers combing the oceanfront site will find anyone alive.

Miami-Dade Mayor Daniella Levine Cava says two additional victims have been found in the rubble of a collapsed condo building in Surfside, Florida, bringing the death toll to 18.

Cava announced the information at a Tuesday evening news conference. Levine Cava says two of the victims were children. She says the number of residents unaccounted stands at 147. 

Earlier on Tuesday, officials confirmed that they had found four additional victims, for a total of six — the highest one-day death toll so far.

She said the personnel in what has become an enormous rescue operation were doing "everything humanly possible, and then some, to get through this tragedy, and we are doing it together."

Colonel Golan Vach, head of an Israeli military unit that specialises in search and rescue operations, told CNN his team had uncovered the bodies as they sifted through the debris, finding what he described as tunnels in the rubble.

In one case, this space was created between balconies of apartments as the building collapsed, he said.

"Between them remained a big space of air," Vach said. "We crawled in those tunnels. We called people and unfortunately we didn't find anything."

READ MORE: 'Deep fire' slowing rescue effort at collapsed Florida condo as toll rises

'Chances are low'

Elad Edri, deputy commander of the Israeli search and rescue team, detailed how rescuers have completed a map outlining the bedrooms and other living spaces in the building where residents could have been trapped.

But he added that "it's been more than six days from the collapsing and the chances to find the lives are low."

He also reported that rescuers had made it to an underground parking structure where it had been hoped they might discover people who had been trapped in cars, but found no one.

The cave-in of the 12-story Champlain Towers South building has sparked a search-and-rescue effort involving engineers and specialists from across the United States and as far afield as Mexico and Israel.

US President Joe Biden will on Thursday visit the site with First Lady Jill Biden to meet with families of the victims.

READ MORE: Anger at Miami disaster response as families demand answers

Over 210 rescuers work on the site

Residents in the part of Champlain Towers South that remained intact reported being awakened around 0530GMT (1:30AM) on Thursday by what sounded like cracks of thunder that shook their rooms.

"It was like an earthquake," said Janette Aguero, who escaped from the tower's 11th floor with her family.

Rescuers who arrived in the moments after the tower came down helped evacuate dozens of residents, and pulled one teenage boy alive from the rubble.

But since then, no other survivors have been found, despite huge numbers of rescuers combing the debris with the help of sniffer dogs and cranes.

Levine Cava said on Tuesday that 210 people were working on the site.

Experts are looking at possible pre-existing critical flaws in the structure of the apartment tower.

An October 2018 report released by city officials last Friday revealed fears of "major structural damage" in the complex, from the concrete slab under the pool deck to the columns and beams in the parking garage.

In a letter to residents in April, Jean Wodnicki, the chair of the condo association, described "accelerating" damage to the building since then.

Repairs had been set to begin soon in the 40-year-old building.

READ MORE: Scores missing as death toll creeps up in Florida condo collapse

Source: AFP