Signals were not operating in Amtrak collision to install crash-avoidance system

— -- An event data recorder has been recovered from the Amtrak train that collided with a freight train this weekend, revealing the moments leading up to the crash, investigators said Monday.

The Amtrak train was headed from New York to Miami when it crashed into the freight train early Sunday in Cayce, South Carolina, just east of Columbia. Two people -- the train conductor and engineer -- were killed, and more than 100 were injured, according to authorities. Eight people remained hospitalized.

The track the Amtrak train was on had been manually switched and "lined and locked," causing it to divert from the main track onto a side track where the freight train was parked, the National Transportation Safety Board said.

The signaling system was not operating at the time because CSX railroad, which operates the tracks, was preparing it for Positive Train Control, a safety technology that can automatically stop trains to prevent crashes.

NTSB chairman Robert Sumwalt told ABC News Monday that PTC could have stopped this collision.

"We're going to go back and develop a complete timeline of this accident," Sumwalt told ABC News.

The event data recorder has revealed this part of the train's timeline, Sumwalt said at a news conference:

-- After the train’s last stop, it followed the speed limit, traveling at a maximum speed of 57 mph
-- About 7 seconds before the end of the recording, the speed was 56 mph and the horn was activated for three seconds
-- Two seconds later, the brake-pipe pressure began decreasing, and the next second, the throttle transitioned from full throttle to idle, while the train was at 54 mph
-- One second later the train's emergency braking was initiated
-- The recording ended 2 seconds later as the train was traveling at 50 mph and its air braking system was approaching maximum braking

"A trained engineer would be able to see the switch-points weren't lined for the track he's intended to be on," Sumwalt told ABC News. "That switch should have been lined so that Amtrak could have continued southbound as planned."

The NTSB said it has interviewed the CSX crew and will interview the surviving Amtrak crew on Tuesday.

The NTSB said its team is expected to remain at the scene until this weekend. A preliminary report will be released in several weeks after the investigators return to headquarters in Washington, D.C., the NTSB said.

Amtrak officials said in a statement that they are "deeply saddened" by the deaths of its employees and that the agency is cooperating fully with the NTSB and the Federal Railroad Administration in the investigation of the crash.

This crash comes just days after another deadly Amtrak accident in Virginia. On Wednesday, a chartered Amtrak train carrying Republican members of Congress to a legislative retreat crashed into a garbage truck at a railroad crossing. One of the three passengers in the trash truck died, authorities said.

When asked today if Amtrak has a system issue, Sumwalt said he was not willing to say that.

ABC News' Daniel Steinberger contributed to this report.