Scores of rescue workers remained on the massive pile of rubble, working to find survivors among the more than 150 people who remain unaccounted for in eastern US city.

Rescue team look for possible survivors in the partially collapsed 12-story Champlain Towers South condo building on June 26, 2021 in Surfside, Florida.
Rescue team look for possible survivors in the partially collapsed 12-story Champlain Towers South condo building on June 26, 2021 in Surfside, Florida. (AFP)

The death toll after the collapse of a Florida apartment tower has risen to nine, the local mayor said, more than three days after the building pancaked as residents slept.

"We were able to recover four additional bodies in the rubble... So I am confirming today that the death toll is at nine. We've identified four of the victims and notified next of kin," Miami-Dade County mayor Daniella Levine Cava told reporters in Surfside, near Miami Beach on Sunday, adding that one victim had died in hospital.

She did not confirm how many people are still missing. Late Saturday officials had said 156 people were unaccounted for after Thursday's collapse.

The 12-storey oceanfront Champlain Towers South pancaked in the middle of the night Thursday as residents slept. Surveillance video of the collapse showed it coming down in just a few seconds.

The rescue operation has been agonizingly slow and painstaking, and fears of a much higher death toll are climbing with each passing hour –– though rescuers have stressed that there may yet be survivors trapped inside the rubble.

READ MORE: 'Deep fire' slowing rescue effort at collapsed Florida condo as toll rises

"My heart is with the community of Surfside as they grieve their lost loved ones and wait anxiously as search and rescue efforts continue," President Joe Biden tweeted on Saturday, offering any federal assistance needed.

TRT World's Yunus Paksoy reporting from the US city said families are still holding out hope their loved ones will be pulled out alive from the rubble.

Frustration and anger at the wait

Families of the missing have expressed frustration and anger at the wait as concerns grown about the building's condition before the collapse.

A study in the 1990s had showed land subsidence in the area, while an engineer's survey of the building in 2018 had pointed to "major structural damage" to a concrete slab beneath a ground-level pool deck, as well as "abundant" damage inside the parking garage.

Authorities have stressed that the reason for the collapse is not yet known, and could take months to determine.

US media have reported that one resident filed a class-action lawsuit against the building's owners seeking compensation for victims less than 24 hours after the tragedy.

READ MORE: Anger at Miami disaster response as families demand answers

Safety audit of older buildings

A lawyer for the building's owners told The New York Times that work was "just about to get started" on the multi-million dollar repairs.

Florida Governor Ron DeSantis told reporters on Saturday that local officials were "considering potentially evacuating" a nearby building that was built by the same developers, around the same time, as the collapsed structure. But he said there were no indications of immediate danger there.

Mayor Cava said the county would immediately undertake a one-month safety audit of all buildings 40 years or older. 

READ MORE: Many feared dead in Miami residential building collapse

Source: TRTWorld and agencies