MIAMI (AP) — The deadly destruction of a Florida beachfront condominium actually started weeks before it collapsed into a pile of rubble in the middle of the night, killing 98 people in 2021, federal investigators found in a final report issued Monday.

The National Institute of Standards and Technology said in the report that two connections between garage columns and the pool deck started to fail around early June. The combination of a structure design that did not meet building codes and alterations made to it over its 40 years meant that the other parts of the pool deck weren’t strong enough to withstand the extra load, leading to the type of slow-motion collapse.

"When building structures are designed and built to required codes and standards, they have margins against failure, meaning they should be able to support much more load than they are expected to bear,” said Judith Mitrani-Reiser, who co-led the investigation. “In the case of Champlain Towers South, these margins against failure were too narrow from the start.”

The report underscores findings that have trickled in since the collapse, which showcase weeks of building distress and deeper-seated problems.

Most residents were asleep when the building in Surfside, Florida, a few miles north of Miami, collapsed into a huge pile of rubble at 1:22 a.m. on June 24, 2021. A Miami judge approved a more than $1 billion settlement for personal injury and wrongful death claims from the disaster.

Harley Tropin, who represented the families of victims and survivors in a class-action lawsuit, declined to comment on the new report.

The structure didn't meet the building codes in place at the time and the building's construction did not follow the design, the report explains. Work done later around the pool — when heavy planters, sand and pavers were added — “further diminished the margins against failure, as did long-term degradation from corrosion,” the report says.

Photos taken by people at the building in the weeks before the collapse show a long crack in a planter wall on the pool deck as well as cracks in the corner where the planter wall met a planter box, according to the NIST report.

Another person told investigators that three weeks before the collapse, part of a gate just down from the planter wall had dipped slightly down, causing it to become jammed, the NIST report says.

The companies responsible for designing and building the original structure in the late 1970s are no longer in operation.

After the collapse, state legislators enacted a law in 2022 requiring condo associations to have sufficient reserves to cover major repairs. Some residents were caught off guard by hefty fees imposed to cover years of deferred maintenance expenses required to bring their buildings into compliance with the law’s standards. That led to another law providing condo associations and residents more flexibility in handling the costs.