Brake failure is being investigated as the possible cause of a luxury train crash in South Africa which killed four people, a safety official says.

The train derailed near the capital, Pretoria, on Wednesday with 55 tourists on board and 30 members of staff.

The victims were all female employees, one of whom was four months pregnant and went into labour at the scene, losing her baby.

According to train owners Rovos Rail, seven people remain in hospital.

Rovos Rail's Rohan Vos said one person remains in a critical condition, the South African Press Association reports.

There were about 40 US tourists, along with French, German and British citizens, on board the Pride of Africa when it derailed.

He told Associated Press news agency that the passengers had been relatively safe in wood-panelled carriages - some dating back to the 1920s - but the staff had been in a kitchen area that was less protected.

Emergency worker Chris Botha at the scene said the railway coaches were lying on top of each other.

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