The deadly 2021 partial collapse of Champlain Towers South in Surfside, Florida, likely began in the condominium's pool deck rather than the residential tower, federal investigators said Tuesday.

The failure killed 98 people and is the subject of an ongoing investigation by the National Institute of Standards and Technology (NIST), which presented new findings this week.

Cracks, water leaks noted before failure

The NIST reported that cracks in concrete slabs, a jammed gate and a sliding glass door that came off its frame were visible in the weeks before the collapse.

The day before the failure, witnesses saw water leaking from the garage ceiling in an area that had undergone repeated repairs.

Investigators said the pool deck and street-level parking deck began to fail at least seven minutes before the tower came down.

Focus on pool deck slab-column connection

Judith Mitrani-Reiser, investigative lead and Glenn Bell, co-lead of the National Construction Safety Team, said computer simulations and structural testing show the failure likely started at a pool deck slab-column connection.

NIST said the team has been analyzing the effects of steel reinforcement corrosion, concrete shrinkage and improperly built joints in the pool deck.

Next steps in investigation

Officials said the investigation team aims to finish technical work by the end of 2025 and release reports, including six subject-focused studies.

Investigators said they are working with construction, inspection and maintenance groups to shape safety recommendations. A detailed public update is expected in spring 2026.