Copper cable theft was believed to be the "root cause" of a passenger train accident near Saulsville in Pretoria on Thursday that resulted in at least 200 people being injured, according to a preliminary finding.
"We have been informed by Prasa [Passenger Rail Agency of SA] that at least 50 metres worth of copper cable was stolen from different parts of the railway track," transport department spokesperson Tiyani Rikhotso said on Thursday night.
"It is the preliminary finding of Prasa that the root cause of the collision can be attributed to the copper cable theft."
Rikhotso explained that when cables are stolen, the rail system's technology changes from automatic to manual.
As a result of the theft, the automated signaling was off.
The train accident happened at around 7am when one train rammed into the back of another, which was stationary.
No deaths were reported, but Prasa said two people, including a train driver, sustained critical injuries. Nineteen others suffered serious injuries. Paramedics examined 350 people, including children, at the scene.
Transport Minister Ben Martins called for a harsh punishment for those found guilty of cable theft.
"Cable theft on our rail lines and system is a serious crime. It deprives our commuters of safe travel on our trains to their various destinations," Martins said in a statement.
"It also destroys infrastructure into which large sums of money are being invested to provide commuters with a safe and reliable public transport service."
He called on law enforcement officers to ensure the perpetrators were brought to book.
The SA Transport and Allied Workers Union believed the train accident was directly linked to the burning of coaches in the past week, and a attack on Prasa members.
"Satawu is concerned that there are serious allegations of sabotage and treachery... by individuals who are associated with the history of hooliganism decoyed as trade unionism," spokesperson Vincent Masoga said in a statement.
"In recent weeks our members at Prasa received threats and some were physically assaulted by a group of hooligans that have [said]... their job is to make all state transport entities ungovernable until a certain NGO is recognised as a union in those entities."
Masoga said their members could not be intimidated any longer.
"Our members and leaders have received deaths threats and constantly been harassed by the same hooligans who are alleged to be behind this attempted treasonous crime," he said.
"The hooligans must be investigated, arrested, tried and be isolated away from our noble society."
Earlier, authorities said a board of inquiry would investigate the accident, which resulted in damage estimated at R22-million.
Prasa planned to compensate the injured with R20-million to cover medical and other bills. The walk-in compensation office would be open on Friday from 9am.
The Democratic Alliance said the accident highlighted the need for an upgrade to Gauteng's railway system.
"The current trains used by the Prasa are technologically outdated and do not adhere to international safety standards," DA MPL Fred Nel said.
"Modern trains can override driver error and prevent accidents like these from happening."
The Congress of SA Trade Unions was shocked by the accident, which it said exposed the working class's struggle to get to work and school each day.
Spokesperson Patrick Craven said while the Gautrain provided a safe, high-class service to the well-to-do minority, the poor risked their lives travelling in an unreliable and unsafe public transport system.
The union federation urged Prasa to tighten its safety measures to prevent further accidents, and to urgently replace its "antiquated trains".
In December, the rail agency awarded a R51-billion contract to France's Alstom SA to supply passenger trains in a 10-year deal. Alstom would build 3600 new train coaches to help overhaul the country's creaking rail network.