In a statement, the Australian Transport Safety Bureau (ATSB) said: 'The driver alighted from the locomotive to inspect an issue with a wagon. While the driver was outside of the locomotive, the train commenced to runaway.
'With no one on board, the train travelled for 92 km before being deliberately derailed at a set of points operated by the control centre, about 119 km from Port Headland (near Turner siding).'
A BHP spokeswoman told The West Australian no one was injured and authorities are investigating.'
'We are working with the appropriate authorities to investigate the situation,' she said.
The ATSB is investigating.