New York's medical examiner's office will search for human remains in an alley where a suspected part of a hijacked September 11 jet is wedged between two buildings.
Police have declared the area a crime scene, at least until forensics experts finish their work.
A piece of landing gear is stuck in a narrow, 60-centimeter gap between an Islamic center and another building in lower Manhattan, close to where the World Trade Center stood. The name "Boeing" and a series of numbers can be seen.
Police say Boeing has confirmed that the apparatus is from a Boeing 767, the type of plane that al-Qaida terrorists hijacked and flew into each tower of the World Trade Center on September 11, 2001.
Police say a rope is tangled around the part, but the reason is not clear.
About 3,000 people were killed in the worst terrorist attack ever on U.S. soil.
Authorities say they may remove the gear on Monday and begin searching for human remains a day later.