SURFSIDE, Fla. (NewsNation Now) — As heartbroken families wait for news of their loved ones, engineers and experts are trying to theorize what could have caused the Champlain Towers building to partially collapse, but nothing fits every clue.

“It just doesn’t happen,” Surfside Mayor Charles Burkett told NewsNationNow.com. “You don’t see buildings falling down in America. And here, we had a building literally fall down. It just doesn’t happen.”

The condo building was due for its 40-year inspection later in 2021. Some residents banded together to retain attorney Sara Shulevitz because of concerns about drilling, water damage and mold.

“One of the residents that was on a very high floor near the penthouse told me there was shaking, that the unit was shaking,” Sulevitz said on NewsNation Early Edition.

So far there have been four confirmed deaths, and at least 159 people are missing.

Experts say it’s too soon to know the cause, but Youseff Hachem, a structural engineer, said it’s probably not as simple as beach erosion.

“They need to look at the plans, the original construction plans at the building to see how the building composition is,” he said. “And they have to be deconstructed. It’s a very difficult process.”

Hachem said inspectors will be doing geotechnical tests to examine the solid under the building.

Beach erosion would have left some obvious warning signs far in advance of its collapse, real estate developer Barry Bodsky said.

“It seems implausible,” he said. “Most of the things that you see in Miami Beach where you see this rebar spalling are from the earlier years when they use beach sand in the mix. When they were pouring the structures in the 1980s, the concrete is considered very clean and pure.”