Clean-up crews have cleared almost all the Rovos Rail coaches from the tracks where they derailed in Pretoria, Metrorail said on Thursday.

Preliminary investigations into the cause of the derailment were still underway and would take at least the next two days, said Metrorail spokeswoman Nana Zenani.

Coaches unhitched, sped downhill

Metrorail would set up a board of inquiry into the incident.

The coaches fell off the rails when they sped downhill while unhitched from the train's electric locomotive which was being routinely removed and exchanged for a steam locomotive on Wednesday.

At the time, the train was on its way from Cape Town to the Capital Park station in Pretoria and was carrying 55 passengers and 30 staff.

Three women employed by Rovos Rail died ? two on the scene and one in hospital. One of the women was four months pregnant and went into labour. Her baby also died.

Ten of the 40 American passengers on board were taken to hospital. Only four of them remained in hospital on Thursday morning. There were also South African, German, British and French tourists on board.

Commuters to be helped

In a statement, Zenani said Pretoria and Johannesburg Metrorail lines other than those affected by the derailment remained operational.

"Metrorail customers travelling from the Pretoria region were this morning [Thursday] able to travel by Metrorail and converge at Bosman Station as a temporary point and were bused from there to Centurion," she said.

Zenani said commuters from Johannesburg could take trains to the Centurion Railway Station from where they were being bused to the Bosman and Koedoespoort railway stations.

Once the track had been repaired, Metrorail would also operate a train shuttle service using diesel (non-electric) locomotives to haul trains between Pretoria and Centurion .

"This will take place on the adjacent tracks which were not affected by the derailment as a temporary link between Pretoria and Centurion while clearing is being finalised," she said.

"This will further eliminate commuter delays and continue the Metrorail service to its customers."

Customers were advised to expect train delays and schedule changes.

Rovos Rail to pay R15m

Rovos Rail incurred damages of R15-million in the incident, its owner Rohan Vos said on Thursday.

"We had insurance and we will now see what happens... the damage amounts to about R15-million," Vos said.

He said Rovos Rail had enough other coaches to continue with its service as normal.

Owner on platform, not on train

Vos said he was standing on the platform in Pretoria when the accident happened on Wednesday morning.

"I was standing on the platform waiting for the train to arrive and was informed about the accident about five minutes after it happened," he said.

An international news agency quoted Vos on Wednesday as saying, "I screamed at the others to jump off... I jumped off while it was moving".

Vos said this was untrue.

The Railway Safety Regular has said it is investigating possible brake failure as the cause of the crash.

"We've reached the stage where we are beginning to interview people who were involved, including the technical staff on the train," said Railway Safety Regulator spokesman Lawrence Venkile.

"We would also want to recreate the accident," he said.

Venkile said investigators were focusing on "whether standard operating procedures were followed to the letter" during the attachment of the locomotives.

"We are also looking at the integrity of the braking system and if it was functioning as it should," he said.

Rovos Rail offers luxurious trips across southern Africa, with a 28-day Cape Town to Cairo trip costing around $56 000.