Heavy damage to the front of a commuter train that slammed into a New Jersey station last month, killing a woman and injuring 100 people, is hampering the investigation into what went wrong.

The National Transportation Safety Board said in a preliminary report Thursday that it has scheduled additional testing after finding that the electronics controlling the train’s brakes and propulsion system were destroyed in the Sept. 29 crash at Hoboken Terminal.

Investigators say other tests showed the train’s air brake system working as designed.

The New Jersey Transit train’s data recorder showed it speeding up and was going twice the 10 mph speed limit just before it crashed. The train’s engineer hit the emergency brake less than a second before impact.

The engineer has told federal investigators he has no memory of the crash.

(AP)