More bodies have been pulled from the rubble of a partially collapsed 12-storey building near Miami, Florida, as the death toll from the incident increased to at least nine on Sunday and more than 150 people remain unaccounted for.

Emergency crews continue to search for potential survivors since the condominium collapsed in the early hours of Thursday in Surfside, a community near Miami. Expert teams from Israel and Mexico also have joined the search.

Miami-Dade Mayor Daniella Levine Cava told reporters on Sunday that the death toll had increased to nine, including one victim who died in hospital.

“We were able to recover four additional bodies in the rubble as well as additional human remains. As of today, one victim passed away in the hospital, and we’ve recovered eight … victims on site,” she said during a news conference.

“So, I am confirming today that the death toll is at nine. We’ve identified four of the victims and notified the next of kin.”

As emergency responders continue to sift through the rubble – a process that was hampered on Saturday by a fire burning amid the debris – questions continue to swirl over what caused the collapse of the condominium.

On Saturday, US media reported that a 2018 engineering report had warned the building was resting on a concrete slab that had “major structural damage” and needed to be extensively repaired. That same report also found “abundant cracking and spalling” of concrete columns, beams and walls in the parking garage.

But it remains unclear what caused the collapse.

Al Jazeera’s Heidi Zhou-Castro, reporting from Surfside, said six to eight squads of rescuers are working through the debris and hundreds of other workers are on stand-by. “Of course there’s a lot of sensitivity here … There’s still hope that there are more survivors buried beneath,” she said.

“We’re now past 80 hours since the collapse, so the news here has not been good although rescue workers are making some progress in the recovery of bodies.”

Federal Emergency Management Agency officials have joined local and state authorities at the site, Florida Governor Ron DeSantis said on Saturday.

DeSantis added that a nearby “sister building” of the collapsed tower is also being looked at because it was built at the same time and with the same design. A voluntary evacuation order has been issued for that other building, and an inspector did not find any immediately obvious problems.

Fire Chief Alan Cominsky told reporters on Sunday that the situation remains “extremely difficult” but that search-and-rescue teams are working “non-stop”.

“We’re doing all that we can, searching all that we can, every bit of hope, to see if we can find a live victim,” Cominsky said, adding that heavier equipment – including cranes – have been brought in. “As we continue, our searches will be modified throughout,” he said.

Meanwhile, families and loved ones of the building’s missing residents continue to anxiously await news. Some families of those missing have provided DNA samples to officials while others recounted narrow escapes.

Police released the names of four victims who ranged in age from 54 to 83.

Building resident Erick de Moura was supposed to be home when the tower collapsed, but his girlfriend persuaded him to spend the night at her place less than 3km (2 miles) away in Miami Beach, likely saving his life.

“Only by God. To me this is a miracle,” the 40-year-old Brazil native told Reuters.(Aljazeera, text excluding headline)

· Scene of Miami Collapsed building and people stop to look at the memorial site created by neighbours in front of the partially collapsed building in Surfside

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