Authorities have asked Washington for additional rescuers to comb the rubble of a collapsed condo tower in an area prone to tropical weather, where 16 people died and no one has been found alive since hours after the collapse.

Members of the South Florida Urban Search and Rescue team look for possible survivors in the partially collapsed 12-story Champlain Towers South condo building on June 27, 2021 in Surfside, Florida.
Members of the South Florida Urban Search and Rescue team look for possible survivors in the partially collapsed 12-story Champlain Towers South condo building on June 27, 2021 in Surfside, Florida. (AFP)

Rescue crews continue to search through the shattered ruins of a collapsed Miami-area condominium tower, with hopes of finding more survivors fading after nearly a week of probing and digging.

Miami-Dade County Mayor Daniella Levine Cava said on Wednesday sixteen people have been confirmed killed in the disaster, which could rank as the deadliest accidental structural failure in US history. 

Another 147 others were still missing and believed trapped in the rubble, he added.

"The way I look at it, as an old Navy guy, is that when somebody is missing in the military, you're missing until you're found, and we don't stop the search," Florida Governor Ron DeSantis told a news briefing on Tuesday.

"Those first-responders are breaking their back, trying to find anybody they can," he said.

But nobody has been pulled alive from the mounds of pulverised concrete, splintered lumber and twisted metal since the early hours of the disaster.

Investigators have not concluded what caused nearly half of the 40-year-old Champlain Towers South condo to crumple as residents slept in the early hours of last Thursday.

But a 2018 engineer's report on the 12-floor, 136-unit complex, prepared ahead of a building safety recertification process, found structural deficiencies that are now the focus of inquiries.

As recently as April, the condo association's president warned residents in a letter that severe concrete damage identified by the engineer around the base of the building had since grown "significantly worse."

READ MORE: Death toll from Miami condo collapse rises as crews continue with search

Special grand jury

Miami-Dade County State Attorney Katherine Fernandez Rundle said she would convene a special grand jury, apart from any potential criminal investigation, to examine building safety and "what steps we can take to safeguard our residents" from similar disasters in the future.

Miami-Dade County Mayor Daniella Levine Cava said search teams extricated the remains of a 12th victim on Tuesday, leaving 149 people listed as unaccounted for. But she said police detectives were conducting an audit of all the missing-persons reports to "verify and remove duplicates wherever possible."

A day earlier she used dire terms in relating how families of the missing were "coping with the news that they might not have loved ones come out alive and still hoping that they will."

"Their loved ones may come out as body parts," she said.

President Joe Biden and his wife, Jill Biden, planned to pay a visit on Thursday to the scene of the tragedy in the oceanfront town of Surfside, adjacent to Miami Beach, the White House said.

Few if any signs of life have been detected in the wreckage since last Thursday.

Fire officials have spoken of hearing faint sounds from inside the rubble pile - they acknowledged such noises could come from settling of the ruins - and finding voids deep in the debris large enough to possibly sustain life.

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

But Miami-Dade Fire Rescue Chief Alan Cominsky said on Tuesday that search personnel faced a daunting task while working in 12-hour shifts in the heat and humidity, hampered by intermittent showers and thunderstorms.

"That building collapsed almost in a footprint of where that building stood – we're talking about 12 stories, with subterranean garages all within that same footprint," Cominsky said.

Debris removed from the rubble pile is being trucked to a collection site to be sifted through by detectives for any bits of evidence that will be cataloged and photographed "for future investigative purposes," Miami-Dade Police Director Alfredo Ramirez said.

Florida emergency management chief Kevin Guthrie said the federal government was asked Tuesday to provide an additional urban search-and-rescue team to aid in the effort. 

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

Source: TRTWorld and agencies