Two former chairs of the National Transportation Safety Board said that investigators trying to determine why an Amtrak train jumped the tracks just north of downtown Philadelphia will focus on video of the tracks and the train's event recorders.
Former NTSB chair Deborah Hersman told "CBS This Morning" Wednesday that investigators will be looking at "the human, the machine and the environment" after the derailment that killed at least seven people, injured more than 200 and plunged screaming passengers into darkness and chaos.
"They're going to be really focused on that operator," Hersman said. "What he was doing, the conditions of the cars and the track and anything unusual that might have been going on right at that point in time."
She also said they'll be looking at the train's recorders for information on how fast it was going.
"The recorders will give them really good information about braking, throttle positions, speed," Hersman said.
Former NTSB chairman Mark Rosenker echoed Hersman's comments, telling CBSN's Elaine Quijano and Meg Oliver that the data recorders will be "very important" to the investigation.
"They are going to let us know exactly how fast that train was moving; if in fact the engineer attempted to apply any braking; whether it was emergency or natural braking capability," he said.
Rosenker said that officials would try to complete the on-scene investigation as quickly as possible so service could be restored on the nation's busiest rail corridor.
"But they will not take any short cuts in order to do that," Rosenker said.
Both Rosenker and Hersman also said investigators will also be looking at video evidence.
"Trains very often have forward-facing video and they'll be looking to see what other trains might have experienced - the ones that went through just minutes or even hours before," Hersman said. "If there were any defects, anything that any of those trains picked up with respect to rough ride or anything that was captured on the video cameras."