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Joe Raedle/Getty Images Miami-Dade Fire Rescue personnel search for survivors
Firefighters are working around the clock to search for survivors following Thursday's partial collapse of the Champlain Towers South Condo in Surfside, Florida.
During a press conference on Friday, officials spoke about the bravery of all those involved in rescue operations, noting that after a "tragic night," the death toll had risen to 4, while the number of people who remained unaccounted for was now 159.
"It's incredibly moving to be on site with these safety personnel, fire rescue. They are totally, totally motivated to find people. They have to be pulled off the shift. That is how motivated they are to continue their efforts," said Mayor Daniella Levine Cava, noting that "this work is being done at extreme risk to these individuals."
"Debris is falling on them as they do their work. We have structural engineers on site to assure that they will not be injured, but they are proceeding because they are so motivated, and they are taking extraordinary risks on the scene every day," she added.
Joe Raedle/Getty The Surfside Condo collapse
Assistant fire chief of operations for Miami-Dade Fire Rescue Ray Jadallah said that a total of 130 firefighters have now been involved in the search. He noted that "this is the risk that we take."
"It's the risk versus benefit. Every time we have that belief that there's hope, with personnel that are trapped, we do risk our lives," he added.
Among those putting their life on the line to help others is Walter Javier, a resident of Surfside and a Miami-Dade firefighter.
"Walter is amazing, he ran to the scene as soon as he heard Thursday around 3 a.m.," his wife Zoya Pashenko-Javier tells PEOPLE. "That's just who he is, and being our neighborhood makes this so much harder than imaginable. He's going back tonight at midnight. Hoping for good news."
A source tells PEOPLE that the collapse has been "devastating" as "many of the firefighters on the scene actually live in Surfside."
"This is devastating for them, knowing what's happening now and what is to come. But they're doing everything they can and will keep going," the source says.
RELATED VIDEO: 99 People Still Missing After Multistory Condo Building in Miami Collapses
During the press conference, Jadallah reiterated that officials remain hopeful that additional survivors will be found.
"We are listening for sounds, it's not specifically human sounds. It could be tapping, it could be steel kind of twisting, it could be kind of the debris raining down," he said. "We have hope."
"And every time that we hear a sound, we concentrate in that area, so we send additional teams, utilizing the devices, utilizing canines, utilizing personnel," he continued.
Added Miami-Dade County Mayor Levine Cava, "We will continue search and rescue because we still have hope that we will find people alive. That is exactly why we're continuing and that is why we're using our dogs and our sonar and our cameras, everything possible, to seek places where there may still be people to be found."
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On Friday, the White House announced that President Joe Biden approved an emergency declaration for Florida, authorizing federal assistance for disaster relief following the Thursday tragedy.
The cause of the collapse remains unknown. During the press conference, the Miami-Dade Police Department confirmed an investigation is ongoing.
Reporting by BECKY RANDEL