NEW YORK: Emergency crews evacuated a busy Manhattan street block during the Tuesday (Jul 7) morning rush hour after structural columns buckled inside a skyscraper undergoing construction work, officials said.The former head office of the drug giant Pfizer, near Grand Central station and the United Nations headquarters, is being converted from offices into apartments in a major overhaul at the 37-story tower.The developer insisted there was no risk of the entire building collapsing. But city officials warned the situation remained serious as they worked to determine if the structure was safe enough to enter to perform remedial work. "Two structural columns have buckled, in addition to multiple cracks and sagging floors. The building remains unstable. Since arriving on scene, we have witnes