The US Federal Aviation Administration has confirmed that a piece of metal that fell to the ground in a Kent, Washington, neighbourhood was part of a Boeing 767's landing gear door.
Witnesses said the refrigerator-size panel hit the ground and skipped about 30 feet before stopping in a street.
No one in the neighbourhood about 15 miles south of Seattle was hurt.
Neighbours said a cargo jet flew low over the area at about the same time the part came down.
Photos on news station KOMO's website show part of an identification plate on the object that has the word "aircraft" along with a serial number.
FAA officials are not saying if they have located the plane that the part came from.