FESA was alerted to the fire at Paint West on Picton Road about 3am last night.

Four fire fighters wore breathing apparatuses to battle the blaze which took more than an hour to extinguish.

Police, Western Power and crews from Bunbury Fire and Rescue and Bunbury Volunteer Fire and Rescue attended the scene.

FESA handed the investigation into the cause of the incident to the arson squad as it was deemed suspicious.

The fire is estimated to have caused at least $100,000 to property in the Picton Road complex.

Neighbouring business owners gathered at the scene this morning, waiting to hear the damage bill.

Knot Just Frames owner Rose Bedggood said her business - next door to Paint West – had suffered collapsed ceilings and significant smoke damage.

“It leaves a sick taste in your mouth,” Mrs Bedggood said.

Midland Monumental owner Jenny Handley said the disruption to business was her main concern.

“I just want to know when I will be able to open again.”