As many as 159 people remained unaccounted for Friday morning, dozens more than officials had previously estimated, as rescuers used trained dogs and sonar in a frantic search through the rubble of the Champlain Towers condo complex in South Florida.
The known death toll had risen overnight to four, officials said, and it remained unclear precisely how many others had been inside the building at the time of the collapse.
Mayor Daniella Levine Cava of Miami-Dade County said officials “still have hope” to find survivors in the tangled concrete, where rescue crews used saws and jackhammers to tunnel through 13 collapsed floors that were stacked like pancakes.
“It feels like a nightmare; none of this feels real,” said Zoila Benezra, a resident of a nearby condo building who was volunteering at a community center where dozens of family members of the missing had gathered on Friday. “Everyone’s just been waiting.”
Rescuers focused their efforts on sounds that came from the pile, but officials cautioned that those sounds may only be from steel twisting or debris raining down.
In an interview on “Good Morning America,” Ms. Levine Cava said the rising death toll was “devastating news for families waiting for any hope of survival.”
The stunning collapse of the residential building, in the beachfront town of Surfside, left few answers and considerable questions about how a 40-year-old condo building could have suddenly crumbled as residents rested in their beds.
The structure, with more than 130 units, was home to a mix of retirees and well-off professionals with young families. The wrecked interiors of what were once people’s homes gaped open toward the ocean: Broken air-conditioning units. An empty bunk bed. Linens waving in the wind.
A lawyer for the resident-led association that manages Champlain Towers said the building had been about to undergo extensive repairs for rusted steel and damaged concrete.
As the search for survivors continued, fire department officials warned that the process would be slow and methodical.
Michael Hernandez, a lifeguard in Surfside, said he spent most of the day Thursday helping comb through the debris, and had been back helping since 3 a.m. Friday.
“I got home and made breakfast and slept for maybe five hours,” Mr. Hernandez said.
When did it happen?
Survivors said they were jolted awake at about 1:30 a.m. by fire alarms, falling debris and the feeling of the ground trembling.
How many people have died?
At least four people were killed. The authorities fear many more fatalities.
How many are unaccounted for?
As many as 159 people were unaccounted for by Friday morning, officials said. The authorities have stressed that the numbers continued to shift as the authorities figure out how many people were actually in the building.
How many have been rescued?
About 35 people were rescued from the intact part of the building, and two were pulled from the rubble, said Ray Jadallah, a Miami-Dade Fire Rescue assistant fire chief.
How tall was the building?
The tower was 13 stories tall; about half of the 135 units collapsed.
When was it built?
It was constructed in 1981, according to county property records.
How many people live in Surfside, Fla.?
The town, just north of Miami Beach, has about 5,600 residents.
As emergency medical workers kept up their frenetic search for the missing in the flattened rubble in Surfside, Fla., on Friday, they relied on some lessons of past disasters and on the grim but increasingly sophisticated science of urban search and rescue.
Michael J. Fagel, an emergency planner, was a scene-safety and logistics officer after both the bombing of the Alfred P. Murrah Federal Building in Oklahoma City in 1995 and the attacks on the World Trade Center on Sept. 11, 2001. He recalled not the noise of the piles, but the silence — the life-or-death importance of utter silence.
“We used stethoscopes. We used hearing devices,” Mr. Fagel, 68, said of the Oklahoma City disaster site. “We would actually stop the mission for five minutes. You’d have three blasts of an air horn. And you would listen. You hear a moan. You hear a whisper. You hear a breathing sound.”
Mr. Fagel, who teaches disaster management, said the search-and-rescue effort in Florida will most likely use some of the same techniques that have guided the response to building collapses and explosions in past decades.
The scene will probably be broken up into zones for easier organization of personnel and in an attempt to instill order. A priority is to cut the utilities, a complex task.
“You may have to go in the street with a backhoe, dig them up, shut them down so you have no more spark, no more potential fuel for the fire,” he said.
There are multiple operations at once, and some move more quickly than others. There are those studying the safety of the scene itself and working to stabilize sections of the building still standing. An acronym soup of local, state and federal agencies and officials assemble, including the task forces that make up the Federal Emergency Management Agency’s National Urban Search and Rescue Response System.
The difficulty for those focusing on the rubble comes in working quickly yet methodically.
“You may remember when you were growing up, there was a game called pick-up sticks,” Mr. Fagel said. “If you pull out something from the debris pile, it may cause a structural shift two floors away.”
And despite all the training and the military-style command structure, each search-and-rescue effort improvises its way through problems.
In July 1981, a dance was being held in the lobby of a Hyatt Regency in Kansas City, Mo., when elevated walkways suspended from the ceiling collapsed, killing 114 people.
As rescuers converged on the scene in Kansas City, streams of water began flooding the lobby. The flow came from water tanks that could not be shut off, and trapped survivors were at risk of drowning. When the fire chief discovered that the hotel’s front doors were keeping the water inside, he called in a bulldozer.
“You use every tool, every faculty, because we are still people helping people,” Mr. Fagel said. “That’s all it is.”
He said some of those searching through the rubble on Friday will remember the work for the rest of their lives. Mr. Fagel, who became ill from working at ground zero on Sept. 11, said the mental and physical effects may not be evident for years.
“I had colleagues of mine who worked the Oklahoma City bombing who would not go back through downtown at Sixth and Harvey,” he said. “They would avoid it. They’d drive around it.
“We as responders put ourselves before others. But we as responders forget that we’re human.”
A young college-age couple. A father and a son. A beloved teacher.
As rescuers continued to comb through debris and rubble for survivors, the friends and family members of those missing in the Surfside building collapse turned to social media in appeals for help.
“Please share we are trying to locate our beloved Lorenzo and his dad Alfredo,” wrote Valerie Pettersen, who described herself as a friend of Lorenzo and Alfredo Leone’s wife.
Arnie Notkin, a former physical education teacher at a nearby elementary school, was remembered as “a great man who devoted his life to Miami Beach” and “a mensch.”
“I’m at a loss for words,” a former student wrote.
“She’s an incredible woman and she will be found! Not giving up hope!”
The University of Chicago chapter of the Chabad-Lubavitch Jewish movement said Ilan Naibryf, a student there and the president of the group’s student board, and his girlfriend, Deborah Berezdivin, were missing.
“They are dear friends, gems whom we love dearly,” the group wrote, adding, “They are both family.”
The 13-story condo building that partially collapsed near Miami early Thursday morning was about to undergo extensive repairs for rusted steel and damaged concrete, an attorney involved in the project said Thursday.
Kenneth S. Direktor, a lawyer who represents the resident-led association that operates the Champlain Towers South building, said an engineer had identified the needed repairs in order for the building to meet structural standards as part of a recertification process for buildings that are 40 years old.
“They were just about to get started on it,” Mr. Direktor said in an interview.
Mr. Direktor said he has seen nothing to suggest that Thursday’s collapse had anything to do with the issues identified in the engineering review. He said any waterfront building of that age would have some level of corrosion and concrete deterioration from exposure to ocean salts that can penetrate structures and begin rusting steel components.
If there had been anything to suggest that a collapse was possible, Mr. Direktor said, the process would have been handled much differently.
“What everyone is going to have to wait for is the results of a thorough engineering investigation,” said Mr. Direktor, who emphasized that the building association was focusing now on helping find survivors and on supporting families.
Government requirements in many parts of South Florida require recertification reviews after 40 years in order to ensure the integrity of older buildings. Anticipating the recertification process at the Champlain Towers South building, which opened 40 years ago, managers had been preparing over the past year for possible repairs, Mr. Direktor said. In recent weeks, he said, the building had started undergoing roof repairs.
Mr. Direktor said engineers had a good idea of where the building needed restoration, but the extent of corrosion is often not clear until crews begin the work.
Charlie Danger, who retired as Miami-Dade County’s building chief seven years ago and helped strengthen Florida’s building codes after Hurricane Andrew in 1992, said that the county began requiring that structural engineers recertify buildings at the 40-year mark after a federal building collapsed in downtown Miami in 1974, killing at least six people.
With buildings close to the ocean, one of the concerns is that improperly protected rebar may rust and lead to concrete spalling, Mr. Danger said.
“If it was a structural failure, what you want is for the inspection to turn up those issues in time to do the work,” he said.
Building inspectors also tend to worry about unpermitted remodeling inside a high-rise unit that might result in the elimination of a structural support column. “If you cut a structural column, your building is coming down,” Mr. Danger said.
One resident at the Champlain Towers complex, Raysa Rodriguez, said tenants have also been wondering about whether impacts from construction on a neighboring complex could have played a role in the collapse. Ms. Rodriguez said the Champlain Towers complex had been shaking from tremors during the construction that was completed last year.
There have been other signs of concern at the complex. In 2015, a resident filed a lawsuit against the condo association, alleging that poor maintenance of the building allowed water to damage her unit after entering cracks through the outside wall. Daniel Wagner, an attorney for the resident, declined an interview but said in an email that the lawsuit related to the “structural integrity and serious disrepair” of the building.
The complex also showed signs of land subsidence in the 1990s, according to an analysis of space-based radar by a Florida International University professor. The 2020 study found subsidence in other areas of the region, but the condo complex was the only place on the east side of the barrier island where the issue was detected.
Kobi Karp, an architect whose firm has worked on a series of prominent buildings in Surfside and Miami Beach, said the way the building collapsed — and the fact that it was only 40 years old — suggested a possible internal failure. He said that might have been caused by deterioration at the point where a horizontal slab of the building meets a vertical support wall, which could lead one of the building’s floors to suddenly fall, bringing the rest of the building with it.
That deterioration, Mr. Karp said, could have either happened slowly, such as over the last few years, or more suddenly if someone unintentionally damaged the structure of the building, such as while remodeling. He said there would have been signs of the structural weakening, like a crack in a wall or floor tiles, but residents may have missed or dismissed the signs, particularly in a condo where many people spend part of the year elsewhere.
Inspectors carrying out the recertification process would be looking for those kinds of flaws as well as rust and other signs of damage, he said.
“The 40-year certification is like a checkup,” he said. “But this is like if I’m 40 years old and in good shape and suddenly I have a massive heart attack and die. We need to find out what happened to cause that heart attack.”
When the Champlain Towers project was proposed in the late 1970s, people were flocking to South Florida and developers were looking to build larger complexes to accommodate demand, said Daniel Ciraldo, the executive director of the Miami Design Preservation League.
Advertisements in The Miami Herald in 1980 touted the Champlain Towers as “elegant condominium residences” that could be had for as little as $148,000.
“Your ultimate comfort has been anticipated: saunas, heated pool, television security system, valet parking and much more,” one ad said. Some of the building’s more than 135 units have recently sold for more than $1 million.
Patricia Mazzei and Alexandra E. Petri contributed reporting.
A partial collapse of the Champlain Towers condo complex killed at least four people on Thursday and forced dozens of others from their homes in the middle of the night with virtually nothing. More than 100 people remained unaccounted for on Friday.
Today, many are searching for ways they can help. The mayor of Miami-Dade County, Daniella Levine Cava, said on Friday that local charities had seen an influx of goods and urged people to donate money instead.
“We have received all of the donations of goods and volunteers that we can handle at this time,” she said. She announced the creation of Support Surfside, a hardship fund. It was established in collaboration with Coral Gables Community Foundation, The Miami Foundation, the Miami Heat basketball team and others.
Ryan Logan, with the American Red Cross, echoed that sentiment on Friday. “We have the supplies we need to help these people,” he said, asking people to donate money to the Support Surfside fund.
The mayor also cited a fund established by The Shul of Bal Harbour, a synagogue, which has already seen more than $450,000 donated. The money will be dispersed directly to the victims and families.
Other charities coordinating donations include the Greater Miami Jewish Federation, which opened an emergency assistance fund. The federation will also provide crisis counseling, social services and more.
The United Way of Miami-Dade has set up Operation Helping Hands to support and assist affected families with both short and long-term needs.
GoFundMe has also created a list of verified fund-raisers for the cause.