The Amtrak train from New York that crashed head-on into a parked freight train in South Carolina early Sunday, killing two crew members and injuring 116 people, had been given verbal approval to proceed down the track, railroad sources familiar with the investigation told NBC News.
But the switch on the track was left in the wrong position, causing the Amtrak train with nine crew members and 136 passengers onboard to drive directly into the CSX train, the sources said.
Amtrak said in a statement that CSX owns and controls the subdivision where the trains crashed, maintains the tracks and signal systems there, and handles the dispatching of all trains.
The CSX signals were down for work and had been offline, the sources said. But verbal permission was given by CSX dispatch to the Amtrak crew to proceed.
Amtrak Train 91 had departed from New York's Penn Station on Saturday and was headed for Miami when it barreled into the CSX train. The crash happened at 2:35 a.m. near a switchyard about 10 miles south of Columbia where autos are loaded and unloaded from railcars.
The CSX freight train was parked on a loading or switch track to the side of the main track, South Carolina Gov. Henry McMaster said. The Amtrak train was moving at about 59 mph when the switch rerouted it to the right.
At a press conference, NTSB Chairman Robert Sumwalt said that for some reason the rail switch was aligned for the train coming down the track to be diverted to the siding, where the CSX train was and hit it head-on.
"Key to this investigation is learning why that switch was aligned that way, because the expectation is that the Amtrak would be cleared and would be operating straight down," Sumwalt said.
The switch that triggered the crash was padlocked in position, which conductors are supposed to do when they move a train from one line to another, Sumwalt said.
Amtrak President Richard Anderson appeared to point the finger at CSX, saying the signal system run by the freight railroad at that spot was down at the time, and CSX dispatchers were manually routing trains.
CSX issued a statement expressing condolences but said nothing about the cause of the accident.
Sumwalt said that positive train control - a GPS-based safety system that can automatically slow or stop trains - could have prevented the accident.
"That's what it's designed to do," he said, referring to technology that regulators have been pressing for for decades with mixed success.
Sumwalt said NTSB investigators will be at the scene over the next few days documenting the accident site and interviewing train crews and dispatchers. He said investigators recovered a camera from the front of the Amtrak train and were looking for the data recorders from the two trains.
The impact of the crash caused the lead engine of the Amtrak train to derail as well as some passenger cars. Video from the scene showed the twisted and gnarled wreckage of several CSX cars.
"I can tell you there's catastrophic damage to each of the locomotives," Sumwalt said. "I can say that the Amtrak locomotive would not be recognizable at all."
Both people who died were Amtrak employees who were in the train engine. The county coroner identified the dead as engineer Michael Kempf, 46, of Savannah, Georgia, and conductor Michael Cella, 36, of Orange Park, Florida.
After the crash, 116 people were taken to four hospitals, according to Gov. McMaster. At least three patients were hospitalized in critical or serious condition, with nearly all the rest treated for minor injuries such as cuts, bruises and whiplash, authorities said.
Palmetto Health emergency room doctor Eric Brown said so many passengers were hurt that they were brought in on two buses, and a tent that had been set up as a waiting room to keep people separate from flu patients was turned into a triage area.
About 5,000 gallons of fuel spilled as a result of the crash and authorities said crews were working to clean it up. Officials said there was no immediate danger to the public.
Jaclyn Kinney, 22, of Pinehurst, North Carolina, said she and her boyfriend were asleep on the train as they traveled to Orlando for a trip to Disney World.
She said they woke up to the crash.
"We got bumped into the wall from the impact and the train derailed," she told NBC via Twitter. "The cafe car that was right in front of us was in much worse shape so we were lucky."
She said Amtrak staff helped them off the train and checked to make sure the passengers were OK.
Kinney said she and her boyfriend suffered minor injuries.
Another passenger, Derek Pettaway, said he was asleep and hit his head on the side of the sleeper cabin during the crash. He suffered a bump on the head, minor whiplash and other bruises.
He described seeing the engine toppled on its side and the cafe car "completely folded in half."
Amtrak officials gathered up luggage and other belongings and within hours put passengers aboard buses to their destinations. Many of them were asleep when the crash happened.
The Red Cross tweeted that "disaster trained volunteers" were responding to the scene of the accident. The National Transportation Safety Board also launched a team to the site. South Carolina emergency officials said that all passengers were off the train by 6:30 a.m.
Before being sent on their way, those who were not hurt were taken to a shelter set up at a middle school, and local businesses provided coffee and breakfast.
"We know they are shaken up quite a bit. We know this is like nothing else they have ever been through. So we wanted to get them out of the cold, get them out of the weather - get them to a warm place," sheriff's spokesman Adam Myrick said.
Lexington County Coroner Margaret Fisher's voice caught as she released the names of the dead.
"Any time you have anything that happens like that, you expect more fatalities. But God blessed us, and we only had the two," Fisher said.
In a statement, Amtrak said that it was "deeply saddened" by the deaths and added that it was cooperating fully with the NTSB, as did CSX. But Amtrak also said CSX maintains all the tracks and signals where the accident happened and controls access to the sidings and yards.
President Donald Trump was briefed on the crash and tweeted his condolences, saying his thoughts and prayers are with the victims. He also thanked first responders for their work.
Amtrak's "Silver Service" is an overnight line that connects New York and Miami with dozens of local stops along the way.
On Wednesday, a chartered Amtrak train carrying Republican members of Congress to a strategy retreat slammed into a garbage truck at a crossing in rural Virginia, killing one person in the truck and injuring six others.
And on Dec. 18, an Amtrak train ran off the rails along a curve during its inaugural run on a route south of Tacoma, Washington, killing three people and injuring dozens. It was going nearly 80 mph, more than twice the speed limit.
After the latest crash, Democratic Sen. Richard Blumenthal of Connecticut said the nation's railroads must be made safer, declaring, "Business as usual must end." He said proven technology, including positive train control, cannot continue to be delayed.
The latest wreck again raised criticism about the safety culture of the nation's passenger railway.
With the string of crashes, "it's becoming almost like an epidemic for Amtrak," said Najmedin Meshkati, a University of Southern California engineering professor who has studied positive train control.
The worst rail tragedy in recent South Carolina history took place in 2005 when a freight engineer parked a train on a side track near a textile mill in Graniteville and forgot to flip the switch back to keep trains on the main track.
A freight train passing through went barreling down the side track and slammed into the parked train, killing nine people, most of them millworkers choked by chorine gas that leaked from a damaged tanker car.
Anyone with questions about passengers on the train can call (800) 523-9101, Amtrak said.
-NBC reporter Tom Costello and the Associated Press contributed to this report.