The 9/11 Memorial Plaza was evacuated after a crane lifting a beam broke some windows at 4 World Trade Center.
A spokesman for Silverstein Properties said a sudden gust of wind caused a steel load to hit the glass on the 45th and 46th floors on the building's south side Wednesday morning.
Some glass fell onto Liberty Street, which was closed at the time.
The 9/11 Memorial closed for the remainder of the day as a precaution.
The New York City Fire Department said no injuries were reported.
The incident came a day after a construction worker was impaled at the site with a small steel rod.
The wound is not considered life-threatening.