The Amtrak train which derailed in Philadelphia late on Tuesday killing at least seven people was traveling more than two times the speed limit when the incident occurred.
Robert Sumwalt of the National Transportation Safety Board said the train was travelling at a speed of 170 kmh shortly before entering a left turn curve where the speed limit is 80 kmh.
Sumwalt added that the engineer of the train applied the emergency brakes but could only reduce the speed to 164 kmh.
At least seven people were killed and more than 200 people injured when Northeast Regional Train 188 going from Washington DC to New York City - carrying 238 passengers and five crew members -derailed in Philadelphia at 9:21 pm on Tuesday.
NTSB said the rail section the train derailed on was not equipped with a new safety system called “positive train control” (PTC) that manages the speed of trains and slows them down if they are moving too fast.
"Based on what we know right now, we feel that had such a system been installed in this section of track, this accident would not have occurred," Sumwalt said.
Federal laws require the national rail network to install PTC system by the end of the 2015, but rail tracks in some areas still do not have it.
"This accident is exhibit A for ending the delays and getting positive train control in place," Senator Richard Blumenthal (D-CT) said.
Philadelphia Mayor Michael Nutter blamed the train’s engineer for the crash.
“Clearly it was reckless in terms of the driving by the engineer. There's no way in the world he should have been going that fast into the curve,” Nutter said.
Sumwalt said the mayor’s comments were inflammatory and refrained from speculating about the cause of the derailment before an investigation is complete.
NTSB said investigators recovered the train's black box data recorders, which contain information such as the speed, track signals and the train’s operation, which are crucial for the experts to determine the reason for the crash.