An 80-foot piece and 40-foot-piece of the crane fell down shortly after 7:20 p.m. The workers had to be pulled from a hole in the ground, fire officials said.
One of the three victims was critically injured, officials said. Another was seriously injured.
A worker at the site said the crane's boom split when a cable that connected it to the body of the crane snapped.
"The cable snapped and the crane boome went down," said the worker, who declined to give his name. "These cables hold the boom up and keep it from going down," he explained of the pully-like system of the crane, which he called a "one-man operation."
Another worker on the site said at least two of the victims were part of the Building, Concrete, Excavating & Common Laborers Union, Local 731.
"You couldn't hear anything else, it was so loud," said Kennon Murphy, 49, who had just left the Javits Center where he was setting up for the car show when the accident occured. "That was crazy. I hate to see something like that happen."