Police investigate shot fired at BHP train

Damage to a moving BHP Billiton iron ore train appears to have been caused by gunfire, West Australian police say.

The train was travelling towards Port Hedland along the company's Mooka line and approaching the staging facility about 6.30pm on Wednesday when forced to stop due to mechanical faults.

On inspection, damage was found, and is believed to have been caused by a firearm.

Anyone who may have observed anything suspicious in the area at the time is asked to contact police.