More than 11 years after 9/11, a piece of one of the planes that hit the World Trade Center towers may have turned up in lower Manhattan. Two law enforcement sources tell NBC New York that the five-foot-long piece of debris was found stuck in a narrow alley between two buildings in lower Manhattan. (One building, 51 Park Place, is the site of the controversial "ground zero mosque.") The plane part, apparently landing gear, has the word "Boeing" stamped on it along with some numbers. The NYPD has now blocked off the area—if the part indeed belongs to a 9/11 plane, one source said, "it would be a crime scene."