Federal investigators announced Monday that the Surfside, Florida, condo building collapse that killed 98 people in June 2021 began three weeks prior to the structure falling.

“Following an extensive technical investigation, the team has concluded that the collapse began in early June 2021, when two connections between garage columns and the pool deck failed,” the National Institute of Standards and Technology’s National Construction Safety Team said in a statement.

NIST investigators said the initial column failures in the Champlain Towers South condominium caused “cracks to grow and loads to redistribute in the pool deck over the next three weeks.”

“This led to the larger catastrophic collapse on June 24,” the NIST safety team said.

The report was released almost five years after the building’s partial collapse.

In September 2023, investigators announced that the construction of the pool deck “deviated from design requirements” and that the “number of slab reinforcing bars centered over vertical columns was inadequate.”

Documents released by Surfside town officials in July 2021 revealed that the pool deck of the condo building and the ceiling of the underground parking garage beneath it had needed repairs as early as 1996.

ABC News previously reported that a 2018 Structural Field Survey report released by the city of Surfside found “major structural damage” to concrete structural slabs on the pool deck and failed waterproofing in parts of the tower.

NIST investigators said on Monday that the agency will now focus on writing the final report.