A team of forensic engineering experts is expected to visit the building site in the Petralona neighborhood of Athens Thursday to investigate any structural or construction failures that may have led to the collapse.

This follows a prosecutorial order to determine whether all provisions of Greece’s building regulations were followed or whether any violations occurred.

According to engineers, there appear to have been several critical failures. They attribute much of the responsibility to excavation work that extended well below the foundation footings of the neighboring apartment building. While the adjacent building’s foundations were approximately 1.5 meters (5 feet) deep, the excavation reached depths of 4 to 5 meters (13 to 16 feet). Engineers say no shotcrete—sprayed, fast-setting concrete typically used to stabilize excavations—was applied to reinforce the neighboring building’s foundations and prevent it from tilting or collapsing. They also point to a number of additional contributing factors.

Engineers stress that buildings do not collapse because of a single cause. Instead, they say, three or four factors usually combine to trigger such a failure. With proper shoring and structural support, virtually any building can be stabilized.

“Buildings Don’t Collapse Overnight”

“Buildings don’t collapse from one moment to the next. We need to determine what went wrong and what compromised the building’s structural stability,” said Andreas Grammatikogiannis, Deputy Mayor for Civil Protection for the Municipality of Athens.

“The required structural support was not installed as mandated by building regulations,” engineers say, adding that the neighboring apartment building also requires a structural inspection after a hole opened in it following the collapse of the four-story building.

Those Arrested Released Pending Further Investigation

A major tragedy was avoided thanks to the vigilance of an elderly resident and the swift intervention of a private engineer, who rushed to the scene after being contacted by the woman’s daughter. Shortly afterward, the four-story apartment building collapsed within seconds while excavation work for the construction of a new building was underway on the neighboring lot. Because the building had been evacuated in time, no one was injured or killed.

As part of the investigation, authorities arrested the project owner, the contractor, the supervising engineer, and two workers. A case file has been opened against them over possible violations of Greece’s urban planning and construction laws. They have since been released while the investigation continues.

Initial evidence suggests that excavation work for the foundations of a new five-story building on the adjacent property may have destabilized the ground beneath the older structure. Investigators believe this may have compromised the building’s structural integrity, ultimately leading to its collapse.