A deliberately lit fire spread to three businesses in the industrial suburb of Webberton on Sunday evening, leaving behind an estimated damage bill of $600,000.
The fire, on the corner of Anderson and Dwyer streets, started just before 5.30pm. Dozens of career and volunteer firefighters rushed to the scene, and it took two hours to bring the blaze under control.
Police were at the scene on Monday morning, with detectives set to investigate.
A DFES spokeswoman said the cause of the fire was deemed suspicious and the damage estimate was $600,000.
She said it had been reported the fire started outside, and spread to the nearby businesses.
One business affected was Penguin 3D Print and Electronics.
The police investigation is ongoing.
Anyone with information regarding the incident is urged to call police.