The subway rail that fractured on Friday under a Manhattan-bound train in Queens had been manufactured in November and installed only two months before the derailment, according to the Metropolitan Transportation Authority.
A thousand passengers had to be evacuated, and 19 of them were injured when the train left the tracks but did not fall over.
Investigators have not yet determined what caused the eight-car F line train to derail in Woodside, officials said Saturday. They were examining the train's maintenance logs, scientifically analyzing the metal rail -- which was examined in March -- and reviewing the actions of the motorman, who underwent routine alcohol and drug testing, said Adam Lisberg, the MTA's chief spokesman.
Lisberg said MTA officials have "no indication that the operator did anything wrong."
Crews using diesel-powered engines, ramps and jacks were working overnight to extricate subway cars from the express tracks at the derailment site, 1,200 feet west of the 65th Street station.
Disruptions to subway service in northern Queens -- along the F, but also the E and the R -- were expected to continue until Monday's morning rush hour, when the MTA hopes service will return to normal in time. There is no express service until then, officials said.
A Long Island Rail Road spokesman said that while the disruption continues, MetroCards will be honored for subway passengers taking the LIRR at Penn Station, Woodside, Kew Gardens, Jamaica and in Brooklyn.
At Elmhurst Hospital Center, which treated 10 of the 19 injured passengers, all but one had been discharged, spokeswoman Atiya Butler said. Details about others passengers sent to different hospitals were not immediately available.
Medics treated passengers for a range of ailments -- including exposure to high temperatures in the tunnel, shortness of breath, chest pain and exhaustion, FDNY spokesman Frank Dwyer said Saturday. No one died or sustained life-threatening injuries in the crash, he said.