AN Amtrak passenger train slammed into a freight train parked on a side track in South Carolina, killing two Amtrak employees and injuring more than 110 people, authorities said.

It was the third deadly wreck involving Amtrak in less than two months.

The Silver Star was on its way from New York to Miami with 150 people aboard around 2.45am (6.45pm AEDT) when it ploughed into the CSX train at an estimated 100 kilometres per hour, Governor Henry McMaster said.

Authorities say the engineer and conductor of an Amtrak train were killed when it slammed into a freight train parked on a side track in South Carolina.

Lexington County Coroner Margaret Fisher identified the people killed as 54-year-old train engineer Michael Kempf of Savannah, Georgia, and 36-year-old train conductor Michael Cella of Orange Park, Florida.

Fisher said the men killed were in the train’s engine. She says she feels fortunate more people didn’t die.

The incident happened around a switchyard about 16 kilometres south of Columbia.

Gov. McMaster said investigators have yet to determine how the Amtrak train ended up on that stretch of track.

“The CSX was on the track it was supposed to be on,” Gov. McMaster said. The National Transportation Safety Board sent investigators.

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.

The only way the Amtrak train could have gotten onto the siding was for a switch to have been thrown, Anderson said.

According to Grasswire, the switch into the siding was still locked with a padlock, which hadn’t been removed after the CSX was moved into the siding.

US President Donald Trump sent his condolences, tweeting: “My thoughts and prayers are with all of the victims involved in this mornings (sic) train collision in South Carolina.”

Mr Trump also thanked “our incredible First Responders for the work they’ve done!”

Officials also said that although 20,000 litres of fuel spilt following the crash, there was no danger to the public.

Gov. McMaster said 116 people were taken to four hospitals. The main hospital in the area had three patients in critical or serious condition, with the rest treated for minor injuries such as cuts, bruises and whiplash, said Dr. Steve Shelton, Palmetto Health director of emergency preparedness.

The locomotives of both trains were left crumpled, the Amtrak engine on its side. One car in the middle of the Amtrak train was snapped in half, forming a V off to one side of the tracks.

“It’s a horrible thing to see, to understand the force involved,” Gov. McMaster said after touring the scene.

Many passengers were asleep when the train began shaking violently and then slammed to a halt, passenger Derek Pettaway told CBS.

“You knew we’d hit something or we’d derailed,” he said.

He added Amtrak staff evacuated passengers in a “really calm fashion.”

Elliot Smith told The State newspaper of Columbia that he was staying with a friend when they heard what sounded like a propane tank exploding. “The sound was so loud, you instantly knew it was bad,” he said. Smith said he and his friend saw passengers limping along the tracks, while others tried to get everyone out of the cars.

Amtrak officials gathered up luggage and other belongings and within hours put passengers aboard buses to their destinations. Before being sent on their way, those who were not hurt were taken to a shelter, 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.

US Senator Richard Blumenthal said the nation’s railroads must be made safer, following the latest crash.

Blumenthal, a Connecticut Democrat, said that as incidents repeat, with injuries and deaths, “inaction is inexcusable.” He says proven technology, including positive train control, cannot continue to be delayed.

Positive train control is a computer system that’s supposed to help avoid excessive speeds in dangerous situations.

Sen. Blumenthal has called for its implementation before. He says “business as usual must end” when it comes to train safety.

It was the third deadly wreck involving Amtrak in less than two months.

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 December 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 130 kilometres per hour, more than twice the speed limit.

The worst train crash 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 the main track. A freight train passing through went barrelling down the side track and slammed into the parked train, killing nine people, most of them millworkers choked by chlorine gas leaking from a damaged tanker car.