Those who required it were to be transported to nearby hospitals for further treatment.
Metrorail spokesperson Lillian Mofokeng said that one train had rear-ended a stationary train at the Germiston station.
"One of the trains was authorised to be stationary there and it was waiting for a manual signal for it to leave the station‚" said Mofokeng.
"We had some cable theft there and that is why we are using a manual system‚" she added.
The incoming train then hit back of the stationary train.
Both trains had commuters on board and were headed for Springs.
Mofokeng said officials were still clearing the railway lines and the train services had in the interim been suspended.