Federal authorities are investigating what caused an MTA commuter train to come off the rails and crash into an oncoming train in Bridgeport, Conn., injuring 72 people during the height of the Friday evening commute.
Fixing the tracks and restoring service "will take well into next week," MTA officials said Saturday afternoon.
Officials have ruled out foul play and are studying a rail fracture.
National Transportation Safety Board member Earl Weener said a portion of the track will be sent to a lab to try to determine if the accident caused the fracture or if the rail was broken before the crash.
The eastbound Metro-North Commuter Railroad train departed out of Grand Central Terminal and was heading to New Haven carrying about 300 passengers when it derailed at 6:10 p.m., according to Metropolitan Transportation Authority spokesman Aaron Donovan.
The derailed train was then sideswiped by another Metro-North train heading to Manhattan and carrying another 400 passengers.
The violent collision near the I-95 overpass sheared roofs off train cars, twisted tracks and sent wreckage flying 200 yards. Three of the injured remained hospitalized Saturday in critical condition, authorities said. There were no fatalities.
"All I know was I was in the air, hitting seats, bouncing around, flying down the aisle and finally I came to a stop on one seat," said Lola Oliver, 49, of Bridgeport. "It happened so fast I had no idea what was going on. All I know is we crashed."
NTSB investigators will be looking at several factors to determine the cause of the derailment, including the condition of the train's brakes and wheels, the track, the train crew's actions and whether signal systems worked properly, Weener said.
"We want our customers to know that while you travel on Metro-North, you can remain confident that your safety, and the safety of our employees, is always the first priority in everything we do," said Metro-North president Howard Permut, who visited the crash site Saturday.
Metro-North, which serves communities in Manhattan, the Bronx, upstate New York and parts of Connecticut, carried 83 million people last year, making it the busiest commuter railroad in North America.
There were 1,261 train derailments in the United States last year, according to the Federal Railroad Administration. Problems with tracks were the cause in 43 percent of those accidents.
The last time a Long Island Rail Road train derailed was on March 13, when a non-passenger train came off the rails near Forest Hills. It took the LIRR nearly a week to repair the damage to the tracks and restore full service.
The last time two LIRR passenger trains collided was in November 2008, when a train engineer failed to obey a signal and sideswiped another train during the morning rush hour near Jamaica. Five minor injuries were reported.