While the main reason behind the collapse of the Miami oceanfront apartment block is still unclear, local officials said the 12-storey tower was undergoing roof construction and other repairs as part of a re-certification process.
Scientists have long warned of the risk of building on barrier islands, such as Miami Beach, which are made of a loose mixture of sand and mud, saying they cannot be developed responsibly, reported NBC News.
The ill-fated Champlain Towers South was located on Surfside, a barrier island town.
"These are very dynamic features. We didn't understand that these islands actually migrate until the 1970s," Duke University professor emeritus of geology Orrin Pilkey told the television network. "As the sea level rises, they move back."
A study published last year in the journal Ocean and Coastal Management found that the Miami Beach area had sunk slightly each year through the 1990s, said NBC News. The study warned that the movement could potentially lead to a rise in coastal flooding hazards.
The condominium had been subject to various inspections recently because of the re-certification process, a requirement under the Miami-Dade County building code for buildings past the age of 40.
An adjacent block was also under construction, Reuters reported.
Although work was being done on the property's roof, court records show that a resident had complained that the building's home owner association failed to repair damage to cracked building walls, the Wall Street Journal reported.
Mr Kenneth Direktor, a lawyer for the condo association, told the newspaper: "Nothing like this (the collapse) has ever happened."
He added: "This is not from surface cracks... There are of course questions about the construction."
In a New York Times report, he noted that the building had undergone upkeep such as concrete restoration and routine repairs over the years, but the association had seen nothing to suggest that the collapse had anything to do with the issues identified in an engineering review.
The review was done by an engineer recently hired by the condo association to develop specifications for changes needed to obtain the re-certification, reported the Miami Herald.
Mr Peter Zalewski, principal of real estate market analysis firm Condo Vultures, told NBC News he had a feeling that an underlying issue might be discovered that could not be assumed right off the bat.
"Forty-year-old buildings don't just collapse, and there is a whole series of them lining up and down the coast," he said.
In 2018, a condo about 2km from Surfside collapsed in a botched demolition project, killing a construction worker, reported WPLG Local 10 News.
