ST. PETERSBURG, Fla. (AP) — Officials don't know what caused a Florida beachside condominium tower to suddenly collapse.

But experts are closely examining a 2018 report that identified numerous issues with the building, including “major structural damage” to a concrete structural slab below its pool deck that needed to be extensively repaired.

The report was among a series of documents released by the city of Surfside.

Rescuers continued to dig Saturday through rubble in an effort to find any of the 156 people who remain unaccounted for after the collapse.

While the engineering report did not warn of imminent danger from the damage, it did note the need for costly repairs to fix systemic issues.

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