Courtesy of Inside NYPD:

A Boeing Company technician confirmed to NYPD Crime Scene detectives yesterday evening that the aircraft wreckage discovered at the rear of 51 Park Place in lower Manhattan last week is a trailing edge flap actuation support structure from a Boeing 767 (see sketch and video attached). It is believed to be from one of the two aircraft destroyed on September 11, 2001, but it could not be determined which one. The NYPD continues to work with the Office of the Chief Medical Examiner as it prepares to sift soil at the location for human remains. When that process is completed, possibly on Wednesday, the NYPD Emergency Service Unit is expected to remove the flap support structure from behind the building to the custody of the NYPD Property Clerk. It will remain there until a decision is made concerning its final disposition. In the past , the National Transportation Safety Board has sometimes taken custody of such parts, or in the case of the 9/11 aircraft, they have been treated as historical artifacts and become part of museum collections. For example, since 2002, the New York State Museum in Albany has in its collection a large landing gear piece that went through the roof to the basement at the same location.