New York Police Department (NYPD) confirmed that the five-foot-long part was discovered by building surveyors between two buildings on the site where a mosque and community center has been proposed three streets away from Ground Zero.
The part bears a "Boeing" stamp, followed by a series of numbers.
Police spokesman Paul Browne said the NYPD had secured the location and would treat it as a crime scene.
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Patchy rain affects northern areas of the UK in the next 24 hours. Elsewhere, dry but rather cloudy.
Marjorie and Micheal Cawdery, both 83, were found dead in their house in Portadown, Northern Ireland on Friday.
Ann Myatt, who is contesting Jo Cox's former seat, told a hustings: "We've not yet shot anybody so that's wonderful."