Amtrak says it has installed automatic train control technology that slows trains on the stretch of track where last week’s deadly derailment occurred. Federal officials have ordered the installment of a more advanced system, positive train control, by year’s end. Full service is resuming on the Northeast Corridor train line today after repairs were made. Federal officials continue to investigate the derailment’s cause amid conflicting accounts surrounding the engineer. After interviewing crew members, Robert Sumwalt of the National Transportation Safety Board said one may have heard the engineer reporting the train was hit by an object.

Robert Sumwalt: “She recalled that the SEPTA engineer had reported to the train dispatcher that he had either been hit by a rock or shot at, and that the SEPTA engineer said that he had a broken windshield and he placed his train into emergency stop. She also believed that she heard the engineer say something about — she also believed that she heard her engineer say something about his train being struck by something.”

Another crew member says he doesn’t recall hearing of anything hitting the train. The engineer himself has spoken to investigators but says he doesn’t recall the moments before the crash.