Wyndham Crime Investigation Unit officers are investigating criminal damage to a business in Hoppers Crossing last month.
A witness was inside a business on Graham Court about 5.30am on 5 February when they heard a loud cracking sound outside.
The witness found the upper floor of the building full of smoke then looked out the window and saw a car parked out the front on fire.
He went outside and found the businesses office area was also on fire so used a hose to put it out before calling emergency services.
The witness did not sight anyone, but a large jerry can was located at the scene.
Investigators have released images of a four door Mercedes sedan seen in the area and a man they believe can assist with their enquiries.