While Cape Town's central train line remains closed due to vandalism, the United National Transport Union (UNTU) on Wednesday warned that it would withdraw the services of its members after four ticket officers were attacked on the city's northern line.
The union's general secretary, Steve Harris, in a statement said it appeared the crime spree plaguing the railway lines had increased on the northern line, referencing the attack near Somerset West station on Sunday.
One employee was stabbed in the head.
Harris said one of the ticket officers involved in the incident had told him she was "petrified" when the four armed men and a woman attacked them on a train.
The woman told Harris: "They started complaining because they had to pay for their tickets. Suddenly they had sharp objects. One of my colleagues was stabbed in the head and started bleeding. When he fell, some of them started to kick him while the others took off the money we had collected and my cellphone from me."
The staffers fled when the train stopped at Somerset West.
The incident was reported to the police, who showed the ticket officers photos of known suspects. They could not identify their assailants from the album.
Western Cape police had not yet responded to a request for further details on the case.
Last month, a recording of a distress call after an attack on a train driver was shared by UNTU at a summit in Cape Town with the Passenger Rail Agency of South Africa's (Prasa) acting chief executive officer Cromet Molepo, Metrorail, police and unions.
The summit aimed to highlight how problems in commuter rail transport were affecting drivers and commuters.
Last year driver Piet Botha was killed at Netreg station while training younger drivers. Four other people, either guards or drivers, have also recently died in incidents related to rail safety.
Last month, staff refused to work on the central line after a guard was killed during a robbery at Chris Hani station, Makhaza, in Khayelitsha.
'City neglected to invite the most important stakeholder'
UNTU at the time said its members would not operate on the line, which serves the Cape Flats, until its members' and commuters' safety can be assured.
"Although an agreement with UNTU was reached within days and they have been ready to resume their duties ever since, Prasa has been unable to resume with services on the central line due to the constant vandalism of the infrastructure."
Harris said Sunday's robbery occurred on the eve of the City of Cape Town's rail summit "with the hope of bringing short-term interventions to stabilise the railway service urgently".
"The city invited Prasa, provincial and national government, but neglected to invite the most important stakeholder, organised labour, who are putting their lives at risk working on these railway lines," Harris said.
"It is of no use to agree on interventions without getting the input from those who are faced with the harsh reality of the situation daily."