"No anomalies" have been found so far when investigators looked at the train braking systems, signals and track geometry, according to a preliminary report released today by the NTSB.
The May 12 derailment of Amtrak 188 outside of Philadelphia left eight people dead and more than 200 injured.
Before the emergency brake system was activated, the train was traveling at 106 mph in an area where the speed is restricted to 50 mph, according to the report.
The engineer activated the emergency brakes "seconds before" the derailment, the NTSB added.
Investigators haven't yet determined if the engineer used his phone while operating the train as they are still analyzing time stamps and video, the NTSB said.
The NTSB said it's also investigating reports of rocks being thrown at trains around the time of the derailment. While there was damage to Amtrak 188's windshield, it's unknown if it was caused by rocks or the derailment. There's also "no evidence" of firearm damage on the windshield, the NTSB said.
The NTSB noted that this report is preliminary and information may be added or corrected as the investigation continues.