Metrorail says the planned resumption of its central line service in Cape Town on Thursday morning has been postponed due to a train derailment between Heideveld and Netreg near the Epping Industrial Area.
Four coaches of a train used for network inspection purposes derailed on Wednesday night.
Technicians are on the scene trying to repair the track and re-rail the carriages.
Metrorail says the recovery process could take several hours and will impact commuters.
The central line was closed last week following the murder of a security guard at the Chris Hani station in Khayelitsha on the Cape Flats.
The 50-year-old guard was providing armed escort when he and another colleague were attacked and robbed of their firearms.
Metrorail says regrettably no buses have been arranged to assist commuters and they are requested to make alternative arrangements until the service resumes.
It says preliminary indications are that vandalism is the cause of the derailment.
A R25 000 reward has been offered for information leading to a conviction.