An investigation has started after a driverless train operated by mining giant Rio Tinto derailed on the outskirts of Karratha.

The incident happened around 6:30pm on Saturday, leaving multiple train cars overturned next to the rail line along Warlu Road.

The mining giant operates around 14,000 cars across its Pilbara rail lines, with each car holding up to 118 tonnes of iron ore.

A Rio Tinto spokesperson said the train was heading to the Port of Dampier from one of its mine sites.

"The incident involved a loaded train, with approximately 30 wagons derailed," he said.

"The safety and wellbeing of our people and communities is our top priority.

"The train was in autonomous mode and no-one was injured in the incident."

The rail line is only used by the mining giant, and does not host other trains.

Work to recover the derailed wagons has commenced and the Office of the National Rail Safety Regulator (ONRSR) has been notified.

ONRSR said initial indications were that the onboard systems governing the automated train safety had functioned as required.