Learners from a nearby school were caught and handed over to authorities.
The train went off the tracks just before 9am near Lentegeur Station on Thursday giving passengers a fright.
Captain FC Van Wyk says a tyre was placed on the rail line.
“According to reports a tyre that was placed on the rail line caused the train to stop under the Morgenster Road bridge. No injuries were reported and no arrest had been made at this stage,” Van Wyk said.
Commuters travelling between Philippi and Kapteinsklip were stranded for one hour.
Metrorail’s Riana Scott says: “The incident happened between Mitchells Plain and Lentegeur Stations. Initial reports attribute the derailment to a tyre placed on the tracks. However, a full investigation is underway.
Eyewitness accounts implicate learners from a nearby school. Metrorail Protection Services officials have handed some learners over to SAPS to obtain their statements on the incident.
“No injuries were reported as a result of the derailment but a woman sustained minor injuries on board when she was struck by a stone flung at the same train shortly before the incident. She was taken to a nearby day hospital for treatment.”
A passenger who was on the train says Metrorail was slow to respond.
“I was working the late shift. When this happened we just walked to Lentegeur Station. We called the Metrorail train incident line and they were not very helpful even after I informed them about the derailed train. A train did, however, come on the opposite track and I got to work on time,” she said.