In the third incident of its type in 11 months, Rio Tinto (ASX:RIO) has suffered a major incident with one of its autonomous iron ore trains in the Pilbara overnight Monday.

Media reports say a train smashed into a set of stationary wagons about 80 kilometres from Karratha in WA's Pilbara region early Tuesday morning.

Rio told media inquirers that no one was injured in the incident, but three locomotives and 22 wagons were impacted.

"We have notified the appropriate regulators and commenced an investigation," a spokesman said.

"Work will soon begin to clear the rail line."

There was no immediate word on whether the track had been damaged and needs repairing or if there would be any delay to Rio's iron ore exports, which this year will run at a rate of more than 900,000 tonnes a day, worth more than $US100 million.

The train was carrying iron ore when it collided with the stationary wagons, though the size of the load is not known, though each of Rio's wagons (it has around 14,000) can carry up to 118 tonnes each.

The collision reportedly happened just after midnight on Monday. It is the third since June 2023.

In February, one of its autonomous trains derailed about 120 km from Dampier port, damaging 38 wagons.

And in June last year, a similar incident occurred with an autonomous Rio Tinto train when as many as 30 wagons left the tracks about 12 miles from Dampier.