FAIRFIELD, Conn. - (CNN) -- Train service in the busy New York-to-New Haven corridor may be restricted for days as officials investigate Friday's rush-hour collision of two trains in Connecticut -- an incident that sent dozens to hospitals -- officials said Saturday.
Officials from the federal National Transportation Safety Board arrived at the site Saturday morning to begin their investigation of the Metro-North train crash in Bridgeport, Connecticut. The wreckage won't be removed until investigators finish examining it on site -- possibly Sunday, NTSB member Earl Weener said -- and then two tracks will have to be repaired before they can be reopened.
While that happens, a long stretch of rail that tens of thousands of passengers take daily will be shut down. That includes Metro North service for a 30-mile stretch between New Haven and South Norwalk, Connecticut, and Amtrak service between New York and New Haven -- both closed indefinitely.
"I think this is going to be with us for a number of days," Connecticut Gov. Dannel Malloy told reporters Saturday morning.
The two Metro-North passenger trains, heading in opposite directions, collided Friday evening in southwestern Connecticut, damaging both trains and leaving some people critically injured.
The accident occurred when a train heading from New York City to New Haven derailed around 6:10 p.m. That train struck the other train in Bridgeport, Connecticut, Weener said Saturday.
Three people still were in critical condition Saturday morning, according to Andrew Doba, spokesman for Connecticut Gov. Dannel Malloy. The governor had said Friday night that five people were seriously injured.
Of the 70 people taken to hospitals Friday, nine remained in the facilities Saturday morning, hospital representatives told CNN.
The damage to the tracks and several train cars is "absolutely staggering," said U.S. Sen. Richard Blumenthal, D-Connecticut, who visited the site with other officials Saturday. Wreckage littered an area of about 200 yards, officials said.
"Ribbons of the sides of cars are torn away like ribbons of cloth," Blumnethal said. "Tons of metal tossed around like toy things. The insides of cars are shattered."
The cause of the derailment wasn't immediately known. Investigators will look at a number of things, including the trains' braking performance, wheel and track conditions, and speed and other information from data recorders, NTSB member Earl Weener said Saturday.
A passenger in a middle car of the New York-bound train, Chris Martin, said his car went dark after the crash.
He then heard someone yell over the intercom for "all the doctors up front."
Martin said his crowded train was evacuated. Everybody on his train was physically fine, he said, but many were shaken emotionally. He said he saw injured people outside the train.
Brian Alvarez said he saw the wreckage.
"I saw this one car and it was completely destroyed, and they were pulling people out of the car," Alvarez said. "... They were all bloody."
Bridgeport Mayor Bill Finch said Friday that travel headaches could persist for weeks because the two tracks affected by the derailment -- which are both "shot right now" -- may take weeks to repair. Cranes will have to remove the wreckage from the tracks once the NTSB has finished its on-site probe.
Because of a bridge replacement project, those two tracks are the only way in and out of New York City by train from that part of Connecticut.
Malloy said the state would set up a system taking rail Metro North patrons from Bridgeport to the closest operable station, in South Norwalk, during the shutdown.
CNN's Susan Candiotti, Rob Frehse, Chris Welch, AnneClaire Stapleton and Jordana Ossad contributed to this report.