• Federal investigators are trying to figure out what role a track switch played in an Amtrak crash that killed two people in South Carolina on Sunday.
• The track at the site of the crash is owned by the freight company CSX. The company says it's installing safety equipment known as positive train control, which the NTSB says could have prevented Sunday's collision.

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Federal investigators are trying to figure out why a track switch at the site of the deadly Amtrak crash in South Carolina was left in a position that caused the passenger train to collide with a CSX freight train.

The portion of the track where the collision happened early Sunday morning had previously been switched to allow the CSX train to reposition, the Post and Courier reported . The switch was locked into position with a padlock, the newspaper said. "Key to this investigation is learning why the switch was lined that way," National Transportation Safety Board chairman Robert Sumwalt said, according to Reuters.

The Miami-bound Amtrak train collided with the CSX train at 2:34 a.m., local time.

Train signals at the crash site that could have prevented the collision were reportedly not operational , because they are being upgraded to install positive train control, Sumwalt said.

Positive train control (PTC) is designed to prevent crashes and derailments . Though Amtrak installs PTC into its own tracks and trains, it also uses tracks that it does not own, and on which PTC may not be installed.

In the case of the CSX tracks where the South Carolina collision occurred, CSX says it will have PTC installed by 2020, but was aiming to get the equipment in place this year, Post and Courier reporter Thad Moore said on Monday .

Although Amtrak has experienced a number of crashes recently , the number of accidents has decreased overall, NBC News reported.