The 5-foot piece is a trailing edge flap support structure, police said. It is located closer to the body of the plane and helps secure wing flaps that move in and out and aid in regulating plane speed. Investigators initially thought it was part of the landing gear because both pieces have similar-looking hydraulics.
Boeing officials told police the part came from one of its 767 airliners, but it isn't possible to determine which flight. Both hijacked planes that struck the towers, American Airlines Flight 11 and United Airlines Flight 175, were Boeing 767s. American and United had no comment.
Workers discovered the part Wednesday on the ground in a sliver of space between a luxury loft rental building and a mosque, which prompted virulent national debate in 2010 about Islam and freedom of speech in part because it's near the trade center site. Other World Trade Center wreckage has been discovered at the buildings and around the area in years past.
An inspector on the roof of the mosque site, which is under construction, noticed the debris and then called 911.
Police documented the debris with photos. The twisted metal part - jammed in an 18-inch-wide, trash-laden passageway between the buildings - has cables and levers on it and is about 5 feet high, 17 inches wide and 4 feet long.
A piece of rope found with the plane part was later determined to have come from a responding officer who used it to move the plane part so he could look for identifying marks.
Of the nearly 3,000 victims of the trade center attacks, remains of about 1,000 were never recovered, and sifting the site for possible human remains was to begin Tuesday morning, said the chief medical examiner's spokeswoman, Ellen Borakove. It's not clear how long the process would take, she said, and details for how workers would comb through silt in the narrow passageway were being worked out.
The area first will be tested as part of a standard health and safety evaluation for possible toxicity, Borakove said.
Police said the part would be moved to a more secure location likely later this week, where a determination will be made about where it will go permanently. In the past, such pieces have been treated as historical artifacts. For example, the New York State Museum in Albany has in its collection a large landing gear piece that fell through the roof to the basement at the same location. It was placed there in 2002.
