Officials with the Port Authority of New York and New Jersey held a memorial mass at St. Peter's Church at 10:30 a.m.
Then at noon, 9/11 Memorial and Museum held its annual ceremony on the National September 11 Memorial Plaza, with a moment of silence at 12:18 p.m.
The attack took place on Feb. 26, 1993, when a bomb built by Islamic extremists exploded in the parking garage of the North Tower of New York's World Trade Center, killing six people and an unborn child and injuring more than 1,000 others, mainly due to smoke inhalation.
Four of the victims were Port Authority employees.
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