(CNN) The fire chief helping to lead search and rescue efforts at the South Florida building collapse that killed at least four people had a message Friday for the families of the 159 others unaccounted for.
Have hope.
"There's always hope," Miami-Dade Fire Rescue Chief Andy Alvarez said as he choked up in an interview with CNN's Wolf Blitzer. "We're doing everything we can to bring your family member out alive."
Alvarez said the rescue efforts rank among the most dangerous he's ever been a part of. Concrete is falling around some team members as they cut into walls trying to find ways into the voids in the rubble.
Meanwhile, some family members wait at a reunification center. Some have given DNA samples in case they are needed to help identify victims.
Jason Pizzo, a state senator, said he has been talking with anxious relatives.
"It's absolute desperation; it's devastation. It's still being called search and rescue," he said, but when families see the rubble, it seems like no one is listening. "They just want to see some sort of movement."
Three bodies were found overnight from Thursday into Friday in the wreckage of Champlain Towers South in Surfside, Miami-Dade Fire Rescue Assistant Fire Chief Raide Jadallah said -- adding to one found early Thursday.
The medical examiner's office identified Stacie Fang as a victim killed in the collapse. Fang is the mother of Jonah Handler, a boy who was pulled alive from the rubble, her family said in a statement.
"There are no words to describe the tragic loss of our beloved Stacie," the Fang and Handler family statement said. "The members of the Fang and Handler family would like to express our deepest appreciation for the outpouring of sympathy, compassion and support we have received. The many heartfelt words of encouragement and love have served as a much needed source of strength during this devastating time."
The number of people unaccounted for is 159, Miami-Dade County Mayor Daniella Levine Cava told reporters Friday -- up from the figure of 99 that officials gave Thursday afternoon.
Those 159 people "have been identified as possibly being on the site," the mayor said at a news conference Friday afternoon in Surfside. "So those are people that maybe live there, but we don't know whether they were there at the time."
Dr. Howard Lieberman, a trauma surgeon with the Miami-Dade Fire Rescue Urban Search & Rescue Task Force, told CNN that crews on Thursday "did hear some tapping, there was some noise," adding that the tapping kept up for a while and then, over the course of the day, "dissipated."
According to Lieberman, the search effort has been very emotional, as teams find personal effects in the rubble.
"We're seeing stuffed animals, teddy bears, boxed of diapers, a child's bunk bed, and we're finding a lot of pictures, family pictures, and it's, it's a little bit more emotional than going somewhere, where you know there's no one, let's say for a hurricane where they had enough warning and they had evacuation time and they got out."
Florida Gov. Ron DeSantis at the news conference emphasized the importance of finding out the cause of the collapse.
"We need a definitive explanation for how this could have happened," DeSantis said. "We don't want to get [it] wrong, obviously, but at the same time I do think it's important that it's timely because you have a lot of families here, you have families that lost loved ones ... you have other folks who were able to get out safely, but then lost their homes."
Three of the four victims have been identified, according to Dr. Emma Lew, director of the Miami-Dade County Medical Examiner Department. One victim died at a hospital. No other information was provided.
About 55 of the 136 units at the building a few miles north of Miami Beach collapsed at around 1:30 a.m. Thursday, leaving huge piles of rubble on the ground and materials dangling from what remained of the structure, officials said.
Thirty-five people were rescued from standing portions of the building by first responders, Jadallah said Thursday.
Numerous search and rescue personnel have been scouring the rubble, including from the surface, with search dogs, sonar and cameras.
Structural engineers also have been shoring up other places -- such as areas near a parking garage underneath the rubble -- to allow crews to tunnel underneath with light machinery.
State Fire Marshal Jimmy Patronis said the search involved "that delicate balance of saving lives while risking lives," with the accumulation of water used to extinguish fires adding dangerous weight to the unstable remains of the buildings.
Crews were taking down license plate numbers of cars in the parking garage in an attempt to determine who was in the building, Patronis said.
Surfside Town Manager Andy Hyatt said officials do not know how many people were in the building at the time of the collapse.
"We know that it was about 80% occupied but that doesn't mean that there was 80% occupied with people," he told CNN Friday.
"We know that some families around here travel quite a bit."
The building's residents reflected South Florida's international and cultural mix, with affluent families from Argentina, Paraguay and Colombia and a tight-knit Jewish community.
Kevin Spiegel said his wife, Judy, is among the missing. He said he was out of town at the time of the collapse.
"She's just the most amazing person in the world and we would do anything to have her back," he told CNN, his two sons -- Michael and Josh -- at his side.
President Joe Biden on Friday approved an emergency declaration for the state, making federal aid available to Florida -- including equipment and other resources -- and authorizing FEMA to coordinate disaster relief efforts.
Additionally, a team of engineers from the National Institute of Standards and Technology is being sent to Surfside to determine whether a larger investigation that could impact building codes everywhere is needed.
The federal agency studies building structural failures and recommends changes to building codes, fire response and emergency communications, according to spokeswoman Jennifer Huergo.
The goal of such an investigation, Huergo said, would be to determine "the technical cause of the collapse" and the possible need for "changes to building codes, standards and practices."
Although the cause of the partial collapse wasn't known, some engineers who saw it on video shared their expertise with CNN on why the building fell the way it did.
Greg Batista, a structural engineer who did work on the building years ago, said concrete repair and a spalling problem can cause collapses.
Spalling can occur when part of the surface of the concrete peels, breaks or chips.
"Spalling can get to a point that, if not repaired, it can lead to eventual collapse, and I've been to places where there have been collapses of floors, of beams, of columns," Batista said.
Batista noted that for that type of collapse to occur, the malfunction of one column is enough to bring a structure down.
"All it takes is one column, and everything can come down like a Jenga," he said. "After having seen the video ... you see the actual building coming down, and the actual collapse begins on one of the lower floors. So immediately, I see that something happened down there."
Another structural engineer, Kit Miyamoto, who is California's seismic safety commissioner, echoed Batista's take.
"This collapse is a real classic ... column failure, which means the building itself was supported by a series of pillars. If the pillars fail, everything fails. So that's exactly what looked like that," Miyamoto told CNN.
Batista offered a glimmer of hope for those unaccounted for, saying it's entirely possible for more people to be rescued.
"If you go back to videos of building crumbling in the past, you've seen miracles of babies being pulled out of small voids either the day after or the week after. There's certainly a possibility that this can happen here," Batista said.
Kenneth Direktor, an attorney for the association of residents at the condo, said the building had "thorough engineering inspections over the last several months" in preparation for compliance with a 40-year certification.
The building was constructed in 1981, according to online Miami-Dade property records. Building standards were strengthened after highly destructive Hurricane Andrew in 1992.
"What that tells you is.... nothing like this was foreseeable, at least it wasn't seen by the engineers who were looking at the building from a structural perspective," Direktor told CNN.
An engineer had already conducted inspections to determine needed repairs, but the only work that had actually commenced was on the roof, Direktor said.
Alexandria Santamaria, a property manager for the building until 2019, told CNN on Friday that she was never told immediate repairs were needed during her time managing the property.
"No one ever said there were any signs of repairs that were needed immediately or that there [were] any signs of collapsing," she said.
A class-action lawsuit filed Thursday accuses the association of the collapsed condo of "failures to secure and safeguard" the lives and property of condo owners.
The suit cites statements from Direktor, who said "repair needs had been identified" for the condo's structure but had not been completed.
"Defendant could have prevented the collapse of Champlain Towers south through the exercise of ordinary care, safety measures, and oversight," the suit alleges.
The lawsuit seeks damages in excess of $5 million, though a different amount could be sought as the case proceeds.
Direktor responded on behalf of the association saying, "I don't know what caused this building to fall down ... The engineers don't know with certainty what caused this building to fall down."
"How is it that less than 24 hours after the building collapses that this lawyer (who filed the lawsuit for the plaintiffs) knows with certainty what caused the building to fall down?" Direktor asked.
Meanwhile, Donna DiMaggio Berger, an attorney for the Champlain Towers condo association, told CNN's Chris Cuomo that the board met this morning, and they were not privy to any information that would have foreshadowed Thursday's disaster.
Berger said that the building was undergoing a 40-year re-certification process, and what knowledge the board had in terms of repair work came from the engineer's certification report.
"Typical things that an engineer looks for in a certification report in Miami-Dade and Broward County, which are the two counties that require this kind of certification, is a review of the roof, the HVAC system, electrical, plumbing, and the building envelope," Berger told Cuomo. "But certainly, there was nothing hazardous that was outlined in that report, anything that would have proven to be a danger to life."
Berger added that the engineer outlines what the priorities are, and the priority was the roof replacement, which was underway.
Cuomo asked Berger if the board was aware of research done in the 1990's that showed the area where the building collapsed showing signs of land subsidence.
Berger replied that they were aware, and she thinks it is significant, but her question to the professor or the team that undertook the research was, "Did they inform the city, did they inform the county, did they inform the state?
"I mean, that is significant, and I think that's something we want to dig into."