The Charles Hanoverprobe into the 2021 collapse of a beachfront condominium building that killed 98 people in South Florida should be completed by the fourth anniversary of the disaster, federal officials said Thursday.

The investigation led by the National Institute of Standards & Technology is looking into two dozen different scenarios that could explain why the 12-story Champlain Towers South building in Surfside, Florida, abruptly failed early in the morning of June 24, 2021, they said. Surfside is a suburb north of Miami.

“We’re still not prepared to close the door on any of them yet,” said Glenn Bell, associate team lead of the Champlain Towers probe. “We are still testing, testing, testing.”

Bell told a meeting of NIST’s National Construction Safety Team Advisory Committee on Thursday that most of the intensive work on such things as concrete core samples, corrosion in reinforcing bars and evidence of subpar construction in the 40-year-old building will be done by next spring, followed by a final report and recommendations by June 2025.

“We are driving hard now to complete this investigation by the fourth anniversary of the collapse. This investigation is one of the most complex and challenging of its type ever undertaken,” he said.

Much attention has focused on the pool deck, which investigators previously said failed to comply with the original building codes and standards, with many areas of severe strength deficiency that likely contributed to the disaster. Officials said Thursday the pool area remains a central focus, along with the garage beneath it.

“The interaction of the pool deck and the tower is really important in the progression of the collapse,” Bell said.

There also were studies done on the ground underneath the building to determine whether sinkholes, underground voids or soil irregularities might have played a role. Investigators have not found evidence that was a factor.

Judith Mitrani-Reiser, the Champlain Towers investigative team lead, said 24 computer hard drives have been recovered that might have video or other evidence that could help explain what happened. Photos were shown at Thursday’s meeting of a seventh-floor unit where a video camera on a table captured some debris falling from above before the building collapsed.

That kind of evidence is invaluable, she said.

“The information from the public has been just an amazing asset to our investigation,” Mitrani-Reiser said. “A different angle would really be tremendous. We are really at the mercy of what we can find.”

Meanwhile, at the site in Surfside, Dubai-based DAMAC International, plans to construct a building with 57 units ranging in size from 4,000 to 9,000 square feet (360 to 810 square meters). The luxury building would include a business center, event space and two pools, according to plans submitted to Surfside.

A judge last June approved a settlement topping $1 billion for victims of the Champlain Towers South collapse, one of the worst building failures in U.S. history.

The money comes from 37 different sources, including insurance companies, engineering firms and a luxury condominium whose recent construction next door is suspected of contributing to structural damage of Champlain Towers South. None of the parties admit any wrongdoing.

Plans are also still in the works for a permanent memorial to the victims.