FORT LAUDERDALE, Fla. (AP) — Federal investigators determining why a Florida condominium tower partially collapsed three years ago, killing 98 people, said Thursday there were many faulty support columns in the tenant garage that ran below it and the adjoining pool deck.

National Institute of Standards and Technology investigators told an advisory panel that tests show that some of the steel-reinforced concrete columns at Champlain Towers South were half the strength they should have been and were not up to construction standards in 1980 when the 12-story tower was built. The steel in some had become moderately to extremely corroded, weakening them further.

Investigators have also confirmed eyewitness reports that the pool deck fell into the garage four to seven minutes before the beachside tower collapsed early on June 24, 2021, in the Miami suburb of Surfside. Thursday’s meeting was in Maryland and streamed online.

Glenn Bell, one of the lead investigators, stressed that the results are preliminary and will not be official until all tests are completed and the final report issued next year.

“The implications of our recommendations are very large, and we feel pressure to get this right,” Bell said. “Bringing about the changes that may be required based on the lessons that we learned may not be easy.”

The federal agency cannot change state and local building codes, but it can make recommendations.

The concrete pool deck was attached to the building, and investigators believe its failure likely damaged and destabilized the base of a support beam that ran through the tower section that first fell. When that beam failed, that caused that tower section to pancake down and a neighboring section to then fall onto it, they said.

The question remains, however, whether the pool deck collapsed on its own or something happening within the building triggered it, they said.

Evidence supporting the theory that the deck failed on its own includes photographs taken weeks before the collapse showing large cracks in concrete planters that lined the pool area. That shows the deck was already under stress, investigators said.

Evidence supporting the idea that something happening within the tower triggered the deck collapse includes surviving tenants telling investigators they heard loud banging from inside the walls before the deck failed.

Pablo Langesfeld, whose 26-year-old daughter Nicole died in the collapse with her husband, Luis Sadovnic, criticized the investigation for taking too long. He pointed out that Miami-Dade County prosecutors have said they cannot determine whether any criminal charges are warranted until the federal investigation is completed.

“I understand the complexities of such an investigation, but almost three years later, 40 employees and around $30 million spent and still not solid answers — it is not acceptable,” Langesfeld said. “It is frustrating that justice, and accountability seems nowhere in sight.”

Lawsuits filed after the collapse by victims’ families and survivors settled in less than a year, with more than $1 billion divided. The money came from several sources, including insurance companies, engineering companies and a luxury condominium that had recently been built next door. None of the parties admitted wrongdoing.