CAYCE — An Amtrak train traveling along the wrong track in Lexington County rammed into the back of a parked freight train early Sunday, killing the conductor and engineer and sending 116 people to area hospitals.

The New York-to-Miami train with 139 passengers collided with an unmanned CSX train on a track at 2:34 a.m. near Cayce. Amtrak President Richard Anderson said the train was traveling at about 60 mph when it wrecked.

NTSB Chairman Robert Sumwalt told reporters that the Amtrak train was switched off the main track to a side track with the parked freight train. The switch was left in the wrong position after the freight train was moved across four sets of track. Sumwalt said early indications point to "tragic human error" and not foul play.

The 36-car freight train had unloaded cars on the far side of the tracks and then moved to the opposite side. As the train was moved across the four tracks, a switch was activated and padlocked so the train could go from the main track to a side track, which is a standard procedure, Sumwalt said.

Investigators found the padlock still on the rail switch Sunday after the collision, Sumwalt said. He did not know why the lock had not been removed after the freight train moved. The Amtrak train was supposed to stay on a track next to the freight cars.

Anderson said CSX owns the tracks and manages the switches in the area where the collision took place. The track signals were not working because of maintenance, Anderson said, but neither the Amtrak boss nor Sumwalt could say if that played a role in the collision.

Sumwalt said a long-delayed nationwide system known as positive train control that could slow speeding trains, prevent head-on collisions and alert engineers to switches set the wrong direction could have helped.

"An operational (positive train control) system is designed to prevent this type of accident," Sumwalt said

Drone footage aired on Columbia TV station WLTX showed the trains near the the S.C. State Farmers Market at the intersection of U.S. 321 and Pine Ridge Road were traveling along the same track when they collided. The lead passenger train engine derailed along with several cars, including a pair in the middle that jackknifed.

The trains were mangled. "I would say the Amtrak locomotive would be not recognizable at all," said Sumwalt, a Columbia native.

Amtrak conductor Michael Cella, 36, of Orange Park, Florida, and engineer Michael Kempf, 54, of Savannah, Georgia, who were in the engine, died from injuries sustained in the collision, Lexington County Coroner Margaret Fisher said.

The wreck jarred awake sleepy passengers.

Samuel Rodriguez from Brooklyn said he woke up just before the crash because he thought the train was traveling faster than it had earlier during his trip to Tampa with his mother that started on Saturday. He said the conductor told passengers at one point that the train was running behind schedule because of freight trains in front of them.

Amtrak 91 was supposed to arrive in Columbia at 1:38 a.m. Sunday, according to an online schedule.

Right when Rodriguez mentioned how fast the train was going to his mother, he felt the train brakes jam: "It was amazing, right when I said that, the car just started going crazy and it was just shaking back and forth."

He saw a toddler fly in the air. His mother's face smacked into the seat in front of her. The seat in front of him twisted sideways.

Screams of pain were followed by what Rodriguez called a chilling quiet. The train car filled with smoke. Rodriguez said he brought the first toddler back to his mother and then helped another toddler, who had a deep cut on his head.

Passengers walked away from mangled train into the cold night air that smelled of fuel leaking from the freight engine.

"Everybody was in shock," he said.

Anderson said though the train was running late, a common occurrence because of freight train delays, the passenger train was not traveling too fast. "That is not how you run a railroad," he said.

Sumwalt said the speed limit is 59 mph in that area of track where the collision took place, though it would have been too fast if a train switched tracks.

National Transportation Safety Board investigators started work at the crash site just southwest of Columbia. An investigation will take 12 to 18 months. The NTSB has recovered the front-facing video camera for the Amtrak train and other recording "black" boxes for both trains.

Inspectors from the S.C. Office of Regulatory Staff, the state agency that oversee railroads, also visited the crash site.

The 139 passengers and six surviving Amtrak crew members were evacuated from the Amtrak train. The collision sent 116 people, including children, to four area hospitals in buses and ambulances. Six were admitted. At least one passenger is in critical condition with another two in serious condition, Palmetto Health officials said.

The nearly 50 patients who arrived at Palmetto Health Richland were screened in a tent the had been set up to handle the recent influx of flu patients. Many passengers were released from all four hospitals after being treated for minor injuries.

The South Carolina Red Cross set up a shelter for more than 30 passengers at Pine Ridge Middle School. Amtrak brought buses to carry passengers to their final destinations.

Some 5,000 gallons of fuel leaked from the freight train but did not pose a public threat, county authorities said.

The wreck revived memories of the deadly 2005 train collision in Graniteville that killed nine and hurt more than 250 people, many of whom were treated for exposure to chlorine gas. In August, a CSX freight train derailed in Lugoff in Kershaw County after striking a bulldozer that was intentionally placed on the tracks.

Sunday's collision took place near the intersection on Interstates 26 and 77, not far from the S.C. Emergency Management Division headquarters where Gov. Henry McMaster and NTSB officials held news briefings on the collision.

The governor visited the crash site about 10 miles away from the Statehouse as well as the Red Cross shelter. He spoke with U.S. Transportation Secretary Elaine Chao.

President Donald Trump tweeted about the crash: "My thoughts and prayers are with all of the victims involved in this mornings train collision in South Carolina. Thank you to our incredible First Responders for the work they’ve done!"