At least ten men were killed and 15 others injured in the sudden collapse of a wing of a four-story office building on October 3, 1956. The failure occurred without warning shortly after concrete had been placed for the top floor of the structure. Speculation at the moment is that the failure may have occurred as the result of punching shear of the flat-plate 10-inch-thick concrete floors at the columns. Although the slabs were integral with columns, the section available for punching shear was reduced substantially by duct and piping openings along some interior columns. The floors were supported on square columns spaced on 24-foot centers. There were no drop panels or column capitals.