A concrete floor collapsed as it was being poured, injuring eight who had been working on the residential building in New Haven, Connecticut, according to news reports.
Two of the workers were in critical condition.
Some workers were rescued from rubble as the second floor collapsed onto the first and into the basement. Some workers had to be lifted out before the concrete hardened.
Video shows the floor with several ride-on trowels deployed, and the section where the floor collapsed.