Transcript for Reason for Florida building collapse still unanswered
First a question on everyone's mind. How could a building this size that has withstood hurricane-force winds for decades crash to the ground in just a matter of seconds? Our Victor Oquendo is also in surfside with more on that part of the story. Victor, good morning. Reporter: Good morning, whit. The immediate priority, it's still on search and rescue then comes the investigation into how half of this building just came crashing down. As search and rescue teams work tirelessly to find survivors, investigators are trying to determine exactly how the Champlain towers south complex collapsed. I know they will have engineers looking at this to try to identify what happened and what was the problematic occurrence. Reporter: The structure built in the 1980s with more than 130 apartments, 55 units were destroyed. Surfside requires buildings to be recertified every 40 years and the town's commissioner says the building has been underscrutiny because of potential construction projects nearby. There have been engineers all over that building to validate that they would be okay for the 40-year recert so how something of this magnitude, which would be somehow structural could have been missed with that much scrutiny is shocking to me and a complete mystery. Reporter: Right now there are few answers. Public records show in 2015, a lawsuit was filed claiming an outside wall had water damage and cracks. This is not just a routine deterioration of the exterior concrete. Reporter: Kenneth derektor says they had hired engineers to go through the inspection process. Nothing like this was addressed to the board or owners as an existing risk. Reporter: The group had been preparing to make up dates and already submitted plans to the city but the only work that had begun was construction on the roof. The mayor says he's not convinced that could have caused the crash, Greg Batista is a structural engineer who worked on the towers in 2017 and was on scene after the collapse. He says he had not heard of any structural issues. I was at the building, you know, a few years ago, it's just bizarre for me to see what happened here because of the rarity of something like this happening. Reporter: Our team spoke with a professor from Florida international university who actually studied this building in the 1990s. He said he was shocked at what he found back then that the building was basically slowly sinking into the Earth and believes whatever caused it to collapse didn't start this year but many years ago. Cecilia. Okay, Victor, thank you so much.
This transcript has been automatically generated and may not be 100% accurate.