Arson causes $200,000 damage to WA trucks

A deliberately lit fire has destroyed agricultural vehicles, causing more than $200,000 worth of damage in Western Australia's South West region.

Police and firefighters were called to a commercial property on South West Highway near Giorgi Road in Picton about 10pm on Saturday.

Several agricultural vehicles were parked next to each other and police believe one of them was deliberately set on fire, which then spread to the others.

Detectives want to speak to a man travelling with three children, who stopped his car at the scene, and anyone else who may have seen something suspicious.