Video released by federal investigators indicates Surfside Condo had extensive corrosion

What they're saying: "The risk posed by 'congested' vertical rebar in columns would have been exacerbated at locations where the rebar overlapped," said Abieyuwa Aghayere, a Drexel University engineering researcher who reviewed the video, per AP.

• He noted how "powdery" and white the concrete in the columns appeared in the video. "The white color just stuns me," Aghayere said in an interview, adding that rather than seeing aggregate material mixed in the concrete, "it's just homogenous" — a likely indication of saltwater damage.
• "The corrosion on the bottom of that column is astronomical,” said structural engineering professor Dawn Lehman, noting the corrosion should have been documented in a 40-year inspection that was ongoing when the building fell.
• "If there’s that amount of corrosion, this should have been fixed," Lehman added.

What's next: NIST said a team will investigate the Champlain Towers South collapse, which will be led by Judith Mitrani-Reiser, the associate chief of the Materials and Structural Systems Division.

• "We are going into this with an open mind and will examine all hypotheses that might explain what caused this collapse. Having a team with experience across a variety of disciplines, including structural and geotechnical engineering, materials, evidence collection, modeling and more, will ensure a thorough investigation,” Mitrani-Reiser said.