A young girl and her mother have visited the site of yesterday's Amtrak train collision in South Carolina to deliver donuts to rescuers working around the clock to clear the wreckage.

"We came out to give cops donuts because it was a special treat for them to come and help people," the girl told local media.

"I hope they get better, and the people that died, we prayed for them in the car. We hoped that they would get better and that they wouldn't have to die.

The girl, who was not named, added that she hoped the "people who died have a good life in heaven".

On Sunday an Amtrak passenger train, apparently traveling on the wrong track, collided with a parked CSX Corp freight train, killing the engineer and conductor and injuring at least 116 people, authorities have said.

Key points: Freight train parked on loading track or side track

Freight train parked on loading track or side track Amtrak train's speed about 95 kilometres per hour on impact

Amtrak train's speed about 95 kilometres per hour on impact 3 patients in critical or serious conditions; rest treated for minor injuries

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

Amtrak Train 91 was carrying 139 passengers and eight crew members to Miami from New York when it hit the freight train about 2:35am on Sunday (local time) near Columbia, South Carolina's state capital, and derailed, the railroad said in a statement.

Killed were Amtrak engineer Michael Kempf, 54, of Savannah, Georgia, and conductor Michael Cella, 36, of Orange Park, Florida, Lexington County Coroner Margaret Fisher said.

Autopsies are under way, she said at a news conference.

Sorry, this video has expired Authorities are investigating how a train appeared to get 'on wrong track' (Photo: AP/Tim Dominick/The State)

South Carolina Governor Henry McMaster said it appeared the Amtrak train was on the wrong track when it slammed into the parked CSX freight train, which had no-one aboard and, "was on the track it was supposed to be on".

The area has three rows of tracks, and the freight train was parked on a "loading track or a side track" and "not the main track," Mr McMaster said.

"It's a horrible thing to see, to understand what force was involved," he said.

"The first engine of the freight train was torn up, and the single engine of the passenger train is barely recognisable."

The number of injured rose to 116 from a previous count of 70, Lexington County spokesman Harrison Cahill said.

Palmetto Health Director of Emergency Preparedness Steve Shelton said three patients were in critical or serious conditions.

The rest suffered minor injuries, like cuts and bruises, Dr Shelton said.

Mr McMaster said he had been told the Amtrak train's speed was about 95 kilometres per hour upon impact but said the National Transportation Safety Board (NTSB) would investigate the crash.

One priority was recovering data recorders from the Amtrak train that would indicate its speed upon impact, NTSB chairman Robert Sumwalt told Fox News.

19,000 litres of fuel have spilled

The lead engine was derailed, as well as some passenger cars. ( AP: Tim Dominick/The State )

TV footage from the crash scene showed the aftermath of the collision, with the Amtrak engine on its side and its front crumpled.

The crash happened near a stretch of tracks by a rail yard about 16 kilometres south of Columbia, where several track spurs split off for freight cars to be unloaded.

Mr Cahill said two leaks of fuel from the trains were secured, and an estimated 5,000 gallons (19,000 litres) of fuel were spilled.

"We have called in DHEC [Department of Health and Environmental Control] and CSX as a team to secure that leak and we are also assisting in that as much as we can," he said.

US President Donald Trump was getting regular updates on the crash while at his resort in Palm Beach, Florida.

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Amtrak officials worked to gather luggage and other belongings and line up buses to take passengers on to their destinations.

Those who weren't hurt were taken in patrol cars to a shelter, and local businesses provided coffee and breakfast.

"We know they are shaken up quite a bit," Lexington County Sheriff's spokesman Adam Myrick said.

"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."

The collision and derailment occurred near Charleston Highway in Cayce, South Carolina. ( Twitter: Lexington Sheriff )

The collision in South Carolina 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 hurtling 80 kilometres per hour over the speed limit.

Reuters/AP