An engineer found evidence of major structural damage beneath the pool deck and "concrete deterioration" in the underground parking garage of a Florida 12-storey condominium in a 2018 report, three years before it collapsed without warning this week as most residents slept.
Search-and-rescue teams were working around the clock on Saturday in Surfside, a shore town near Miami, through an unstable mountain of debris looking for the 159 people still unaccounted for, though the prospects of recovering further survivors appeared to be growing dimmer by the hour.
The death toll, now at four, was certain to rise, with each floor of the high-rise stacked atop another like pancakes and smoke still in the air from smouldering fires. Aided by dogs, cameras, sonar and heavy equipment, rescuers looked for any spaces that may have formed in the debris, leaving possible survivors air to breathe.
"We have hope because that's what our search-and-rescue team tells us, that they have hope," Miami-Dade County Mayor Daniella Levine Cava told a news conference on Friday.
The engineer's 2018 report, released by town officials, was produced for the condominium board in preparation for a major repair project set to get underway this year.
It was not immediately clear whether the damage described in the report was in any way connected with the building's collapse around 1:30 a.m. ET (0530 GMT) on Thursday.
Vice mayor Tina Paul called the structural issue identified in the report “very alarming” in an email on Saturday morning.
The engineer, Frank Morabito, warned that the waterproofing installed below the pool deck had failed due to a major error in design.
"The failed waterproofing is causing major structural damage to the concrete structural slab below these areas," he wrote. "Failure to replace the waterproofing in the near future will cause the extent of the concrete deterioration to expand exponentially."
In addition, Morabito said concrete columns, beams and walls in the garage were showing "abundant cracking," including areas underneath the pool with "exposed, deteriorating rebar." Morabito could not be reached for comment on Friday evening.
Morabito's firm submitted an 84-page document to the town in April detailed a "40-year building repair and restoration" plan for the Champlain Towers South condominium, which was built in 1981.
The condominium was preparing to go through recertification this year, a safety requirement for buildings that reach 40 years of age in Florida.
Satellite data from the 1990s showed the building was sinking between 1 and 3 millimetres per year, while surrounding buildings were stable, according to Florida International University professor Shimon Wdowinski.
He said the data could suggest a structural compromise within the building, though it could also have signaled the building was settling into the soil.
'YOU GOTTA HAVE HOPE'
While local officials provided aid and comfort to the families, such as hotel rooms and food, search-and-rescue specialists worked the disaster site on a rotation, with a limited number allowed at any one time to prevent further collapse.
Teams from Mexico and Israel arrived to help relieve the locally based crews, many of whom have also traveled to disaster sites around the world.
Atop the pile, some wielded hammers and picks looking for signs of life. Heavy equipment scraped away the top layer.
Below ground, rescuers who entered through the parking garage risked their own lives searching for survivors, occasionally being hit by falling debris, officials said.
Miami-Dade Fire Rescue chief Andy Alvarez recalled that his team once pulled a girl out of earthquake debris in Haiti eight days into the rescue effort.
"You gotta have hope. We're doing everything we can to bring your family member out alive," Alvarez told the loved ones of the missing on CNN, pausing as he was overcome with emotion.
The disaster occurred early on Thursday morning, when a large section of the 40-year-old building crumbled to the ground.
Video captured by a security camera showed an entire side of the building suddenly folding in two sections, one after the other, throwing up clouds of dust.
The building had more than 130 units, about 80 of which were occupied, officials said. Roughly half appear to have collapsed.