The cause of Friday’s Metro-North Railroad train crash that injured about 70 people in Fairfield, Conn., may not be known for at least another week as National Transportation Safety Board investigators look into the collision.

The NTSB said there’s no reason to believe the crash was anything more than an accident, and it has yet to label the collision. The agency will look at the conditions of the tracks, the trains’ brakes, and the recorders that were housed inside the two locomotives that track speed and other data. The recorders were sent to the NTSB’s Washington, D.C., offices.

National Transportation Safety Board member Earl Weener said the trains involved in the collision were among the newest in the Metro-North fleet.

"This is the first time a car like this has been involved in this kind of accident; by all appearances, they responded well," Weener said.

A team of NTSB investigators arrived at the crash site Saturday morning, the agency said on its Twitter account.

U.S. Sen. Richard Blumethal, D-Conn., toured the site Saturday morning and described the scene for CNN.

"Ribbons of the sides of cars are torn away like ribbons of cloth," he said. "Tons of metal tossed around like toy things. The insides of cars are shattered."

Two Metro-North trains headed in opposite directions collided with each other in Fairfield during Friday night’s rush hour, sending about 70 people to the hospital. The collision caused one of the trains, a Metro-North locomotive headed for Grand Central Terminal in New York City, to derail at around 6:10 p.m. Friday. About 700 people were on both trains when the collision occurred.

Most of the injured were treated and released from Connecticut hospitals Friday night, according to Dannel Molloy, the state’s governor. Five of the wounded were critically injured.

Metro-North serves the suburbs of Connecticut near New York City and the city's northern suburbs.

Investigators expect the investigation to take between seven and 10 days, Newsday reported.

Metro-North train service on the New Haven Line has been suspended between South Norwalk and New Haven “until further notice” due to the collision, according to the Metro-North Twitter account. Commuters were told to make alternate plans for Monday’s commute.

“This will remain until the investigation and restoration are complete,” Metro-North tweeted.

The collission also has caused delays on other Metro-North lines, according to the Metropolitan Transit Authority, which runs the railroad.

"Customers should anticipate crowded trains due to reduced service, and, if possible, use the Harlem Line as an alternative," the agency's website said.

Molloy would not give an exact timetable for the resumption of normal service.

“I think this is going to be with us for a number of days,” he said, according to CNN.

Bill Finch, the mayor of Bridgeport, Conn., said it may take weeks to repair the tracks.

Bridgeport resident Lola Oliver, 49, who was on the derailed train, described what it was like inside the locomotive during the crash.

"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," she told the Associated Press. “ "It happened so fast I had no idea what was going on. All I know is we crashed."