( CNN ) -- Federal investigators ruled out foul play in a commuter train derailment in Bridgeport , Connecticut , that left more than 70 people injured and shut down service along the busy New York-to-New Haven corridor , officials said Saturday . National Transportation Safety Board investigators are now focusing on a broken rail as a possible cause behind Friday 's rush-hour collision of two trains . `` It is of substantial interest to us , and we will be sending a portion of that track back to the laboratory in Washington , D.C. , for analysis , '' Earl Weener of the NTSB told reporters Saturday . Weener said the fracture could have been caused by the accident itself , or it could have been broken before the trains collided . Investigators will also look at the trains ' braking performance , wheel and track conditions , and speed and other information from data recorders , he said . In addition to the trains , investigators also are examining the behavior and actions of the crew . The wreckage wo n't be removed until investigators finish examining it on site -- possibly Sunday , 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 . 'Absolutely staggering damage ' 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 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 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 . 'Doctors up front ' 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 .
NEW : NTSB investigators are focusing on a fractured rail . NEW : ` ` It is substantial interest to us , '' an NTSB official says . 'New York Times reporter Michael Barbaro reports that the investigation has been delayed because of concerns about safety and cost. " Hospitals say they have treated 70 people .