Regarding Monday's incident where a piece of metal pierced through the floor of an uptown 2 train:

Transit officials say they now believe that a section of rail that pierced the bottom of a subway car on Monday was a damaged piece that had been taken out of service and was sitting on the track bed for more than a year, waiting for pickup.

Employees are working around the clock along the entire length of the subway system to inspect other scrap rail pieces stored on the track bed for any signs of cracking or other damage, officials said yesterday.

"Any rail that is found to be cracked or damaged will be moved off to the side and later removed from the system," said Charles F. Seaton, a spokesman for New York City Transit.

From the NY Times: Disused Rail Lay for Year on Track Bed Before Accident by Michael Luo