After another fatal Amtrak train crash Sunday, safety advocates and federal investigators are again expressing concern about the slow pace of railroads installing and implementing technology that could prevent some train collisions.

Some are also raising questions about what they contend is a "lax safety culture" at Amtrak, which has now had four fatal train accidents in less than two months' time.

National Transportation Safety Board investigators are on the scene of Sunday's wreck in Cayce, S.C., trying to figure out why Amtrak train No. 91 traveling south from New York City to Miami was diverted onto a side track early Sunday morning, where it collided head-on with a parked freight train at about 2:45 ET, killing two crew members and injuring more than 100 passengers.

NTSB Chairman Robert Sumwalt says a switch on the track had been manually padlocked into a position that steered the Amtrak train from the main southbound line track onto a side track, where the CSX train was parked.

Amtrak's CEO is wasting time no time in placing the blame on CSX, which owns, operates and controls the tracks Amtrak uses in the area.

Reuters is reporting that in an email message to staff Sunday night, Amtrak President and CEO Richard Anderson said the passenger train was "on the track as dispatched by CSX, the host railroad... our crew on 91 was cleared to proceed by CSX dispatch, but CSX had lined and padlocked the switch off the mainline to the siding, causing the collision."

Regardless of why the train was sent onto the wrong track, Sumwalt says an automatic GPS-based safety system called positive train control would very likely have kept the two trains from colliding, had it been installed and implemented.

"An operational PTC system is designed to prevent this kind of accident," said Sumwalt at a media briefing Sunday night.

Back in November, at an NTSB meeting to announce the results of the investigation into a fatal Amtrak crash in April 2016 outside Philadelphia, Sumwalt blasted the railroad for its "lax" attitude toward safety, saying "Amtrak's safety culture is failing, and is primed to fail again."

That warning seems prophetic now with the four deadly Amtrak accidents since December.

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