"Unfortunately, in the short period of the illegal strike the drivers from the skeletal bus service were intimidated and are unhappy to continue working," spokesman Errol Braithwaite said.

"The disciplinary procedures that started yesterday, [Thursday] are currently underway and we hope it will be completed by the end of business today so we can discuss the way forward."

Braithwaite said they had locked the striking drivers out of the depot in Midrand.

"We are not going to let them in until the issues are resolved. It is difficult to have meaningful discussions with the drivers who are not represented by a union anymore," he said.

The Gautrain bus drivers, who used to be members of the SA Transport and Allied Workers' Union (Satawu), had left the union and were now acting independently. Satawu confirmed this on Wednesday.

Braithwaite said they could no longer tolerate the behaviour of the drivers who held the company and customers at ransom by acting outside the law.

On Wednesday afternoon, the drivers ignored an ultimatum that required them to return to work by 3pm. A court interdict was issued last month compelling drivers to return to work.

Braithwaite said the drivers launched their own court application to block disciplinary hearings but their application was dismissed by the Johannesburg Labour Court. Some of the drivers were fired.

Last month, drivers went on strike because they wanted MegaExpress -- the Gautrain bus operating company -- to provide them with transport from their homes to their place of work every day.