Perhaps it was a fatal flaw in the pool deck that over decades weakened a supporting concrete slab, or a rising sea that drove corrosive saltwater against critical columns in the lower-level garage.

Maybe concrete throughout the building had been poured too thin to protect reinforcing steel, or condo owners and town officials hoped for the best when they should have prepared for the worst.

In the days since the collapse of the Champlain Towers South condominium near Miami on June 24, victims, families, and a shocked nation have pondered those theories and others in a vain search for an answer to the same, desperate question.

What happened?

Yet the only consensus among 10 engineers and other experts interviewed by USA TODAY is that an answer will take time.

“This will be a fact-finding – not fault-finding – technical investigation,” said James Olthoff, director of the National Institute of Standards and Technology, in a press briefing Wednesday to announce that agency’s investigation. “It will take time, possibly a couple of years. But we will not stop until we determine the likely cause of this tragedy.”

In the end, experts said, it will likely be a combination of many factors and missed opportunities that ended in what could become the deadliest building collapse in American history not caused by a terrorist act or natural disaster. The confirmed death toll stood at 22 on Friday, and 126 people were still missing.

“Whether this particular building succumbed to some shortcoming in practice and construction, we just don’t know,” said Glenn Bell, former president of the Structural Engineering Institute of the American Society of Civil Engineers, who has investigated building failures.

But even as the investigation begins, engineers, scientists and regulators elsewhere are seeking lessons from what’s known so far.

“The engineering community will look at this and hopefully learn a lot from it to minimize the chance of this happening in the future,” said Reginald DesRoches, provost of Houston’s Rice University and a civil and structural engineer.

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