Bushfire warning in WA's Pilbara region

An out-of-control and unpredictable bushfire in Western Australia's Pilbara region has prompted advice to locals to remain alert.

The Department of Fire and Emergency Services says the fire, which started south of the Brockman Rail Line in the Shire of Ashburton and was reported at 7.37pm, is moving fast in a north-northeasterly direction toward Hamersley Station homestead.

There is no threat to lives or homes but thick smoke poses a danger for drivers along the Tom Price-Karratha Rio Tinto Rail Access Road and anyone with a respiratory condition.

Firefighters are on the scene.