NTSB Member Robert Sumwalt on the scene of the Amtrak Train #188Derailment in Philadelphia, PA (National Transportation Safety Board)
NTSB Recorder Specialist Cassandra Johnson works with officials on the scene of the Amtrak Train #188 Derailment in Philadelphia, PA (National Transportation Safety Board)
The NTSB Go Team arrives on the scene of the Amtrak Train #188 Derailment in Philadelphia, PA (National Transportation Safety Board)
National Transportation Safety Board member Robert Sumwalt briefs the media in Philadelphia, Pa. (National Transportation Safety Board)
National Transportation Safety Board member Robert Sumwalt briefs the media in Philadelphia, Pa. (National Transportation Safety Board)
National Transportation Safety Board member Robert Sumwalt on the scene of the Amtrak train 188 derailment in Philadelphia, Pa. (National Transportation Safety Board)
NTSB IIC Mike Flanigon briefs Vice Chairman Dinh-Zarr on the scene of the Amtrak Train #188 Derailment in Philadelphia, PA (NTSB)
Emergency personnel gather near the scene of a deadly train derailment, Wednesday, May 13, 2015, in Philadelphia. (AP Photo/Mel Evans)
Emergency personnel gather near the scene of a deadly train derailment, Wednesday, May 13, 2015, in Philadelphia. (AP Photo/Mel Evans)
Emergency personnel help a passenger at the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/Joseph Kaczmarek)
Emergency personnel help a passenger at the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/Joseph Kaczmarek)
Emergency personnel work the scene of a deadly train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/ Joseph Kaczmarek)
A crime scene investigator looks inside a train car after a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/Joseph Kaczmarek)
Emergency personnel work the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/Joseph Kaczmarek)
Emergency personnel work the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/Joseph Kaczmarek)
Officers gather at the scene of a train crash Tuesday, May 12, 2015, in Philadelphia. An Amtrak train headed to New York City derailed and crashed in Philadelphia. (AP Photo/ Paul Cheung)
Emergency personnel transport a person at the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/ Matt Slocum)
Emergency personnel transport a person at the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/ Matt Slocum)
Officers gather at the scene of a train crash Tuesday, May 12, 2015, in Philadelphia. An Amtrak train headed to New York City derailed and crashed in Philadelphia. (AP Photo/ Paul Cheung)
Emergency personnel transport a victim at the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/ Matt Slocum)
Emergency personnel help a passenger at the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. (AP Photo/ Joseph Kaczmarek)
Officers survey the scene of a train crash Tuesday, May 12, 2015, in Philadelphia. An Amtrak train headed to New York City derailed and crashed in Philadelphia. (AP Photo/ Paul Cheung)
Emergency personel work the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. An Amtrak train headed to New York City derailed and crashed in Philadelphia. (AP Photo/ Matt Slocum)
Emergency personel work the scene of a train wreck, Tuesday, May 12, 2015, in Philadelphia. An Amtrak train headed to New York City derailed and crashed in Philadelphia. (AP Photo/ Matt Slocum)
A passenger is carried following an Amtrak train crash Tuesday, May 12, 2015, near Philadelphia. Train 188 was traveling from Washington to New York City. (AP Photo/Paul Cheung) (AP Photo/ Paul Cheung)
An Amtrak train crashed Tuesday, May 12, 2015, near Philadelphia. Train 188 was traveling from Washington to New York City. (AP Photo/Paul Cheung) (AP Photo/ Paul Cheung)
Passengers of an Amtrak train that crashed gather Tuesday, May 12, 2015, near Philadelphia. Train 188 was traveling from Washington to New York City. (AP Photo/Paul Cheung) (AP Photo/ Paul Cheung)
Vehicles surround the scene of an Amtrak train crash Tuesday, May 12, 2015, near Philadelphia. Train 188 was traveling from Washington, D.C., to New York City. (AP Photo/ Paul Cheung)
A passenger from an Amtrak train that crashed is helped Tuesday, May 12, 2015, in Philadelphia. Train 188 was traveling from Washington to New York City. (AP Photo/ Paul Cheung)