One of the train's carriages burst into flames after the accident in a rural area 110 miles south-west of Johannesburg.
A train service official quoted by Reuters said the death toll had risen from four to 14, while South Africa's transport minister said at least 12 people had died and more than 260 were hurt after the Port Elizabeth-Johannesburg train hit a vehicle near Hannema.
"It is not yet confirmed but the death toll for now is sitting at 14," said Daisy Daniel, a spokeswoman for passenger rail service Shosholoza Meyl.
Video of the crash in Free State province showed fire and smoke billowing from at least one carriage, with part of the train derailed and overhead power lines damaged.
A large vehicle was left upside down beside a train carriage that appeared to have partly crushed another, smaller vehicle.
Passengers, some of whom were said to be heading home after the New Year break, were seen with their luggage on the side of the road close to the wreck.
Survivors told how they attempted to save fellow passengers trapped on the burning train.
“I saw around 12 cars on their side and one was already burning. We heard some women screaming when we came closer‚ so a few of us climbed over the cars to investigate,” Tiaan Esterhuizen told TimesLIVE.
“Two of the women were sort of on top of each other. Another was further back. Her legs were trapped. One of the women was shouting that there was a baby inside also‚” he said. “We searched but could not find the child.”
He added: “One man’s back was burned‚ others just had singed clothing. I am not really sure how the car was also involved.
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