"Human error" might have caused Monday's Metrorail accident in which one person was killed and almost 250 others were injured.
Metrorail described the train accident as similar to that of a driver skipping a red light.
Metrorail spokesman Lillian Mofokeng said 177 patients had been discharged from hospital, with 66 others remaining in hospital for observation.
She said Metrorail would open an inquiry into what led to the accident.
"At this point the preliminary findings point to a human error; the driver passed a red light signal. That's the same as a car driver skipping a red light," said Mofokeng.
"We don't know exactly what made him pass that red light but we are going to institute a board of inquiry to find out and get to the bottom of what happened," she said.
Mofokeng said Metrorail had been in contact with the family of the man who died and was providing emotional support and counselling.
She said despite the latest accident, and two other accidents last year that also recorded high numbers of injuries, travelling by rail was still one of the safest means of transport.
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