The leg was found over the weekend on one of the Line 4 tracks, in the Concourse neighborhood of the Bronx. The New York medical examiner's office is examining it to learn more and try to solve the mystery.
Thousands of objects are lost every month on the city's transportation service and later found, including more common things like urns, welder's masks and blenders. Line 4 of the metro service was stopped for a few hours after the discovery, but resumed operations in the afternoon of the same day.