According to a Florida International University professor who co-authored a study focused on the issue last year, the complex had been sinking into the earth bit by bit since the 1990s, at one point at a rate of about 2 millimeters per year.

The Champlain Towers complex in Surfside, Florida, was the subject of at least one lawsuit over the maintenance of the structure’s outer walls. In addition, the building attracted the attention of scientists alarmed over flooding and land erosion.

Kobi Karp, an architect who has practiced in Miami since the late 1980s, said the construction method used in South Florida has been the standard since the 1920s, and it is “the most structurally sound and safest way to build structures, whether it’s a two-story home or a high-rise.”

“So even a building built in the 1980s is a relatively young building,” Karp told The Daily Beast, adding that the event that led to the building’s collapse “could have occurred in the past 24 hours or in the past 24 months.”