A Shetland Transport trailer was set on fire and destroyed last week while it was parked up outside the firm's Aberdeen depot.
A spokeswoman for Grampian Police, which is investigating the attack, described it as a "wilful fire raising" - which under Scottish law refers to circumstances where property is set on fire deliberately with criminal intent, similar to arson.
The trailer was attached to the unit at the time of the fire at 1.45am on Wednesday morning, but the driver was not sleeping in the cab.
Jackie McPhearson, the manager of the Shetland Transport's Aberdeen office, says an accelerant such as petrol was apparently used in the attack. He adds that the curtains in the cab were drawn so that whoever started the fire was probably not certain that there was nobody in the cab.
McPhearson adds: "There has been quite a bit of this sort of thing in Aberdeen lately. It just seems as if it is gangs of kids wandering around at night. The trailer was a write-off."
He says that Shetland Transport fits as many vehicles as it can into the yard, as opposed to outside on the road, but that sometimes there is not enough room for every truck.
Grampian Police say they are unaware of any wider pattern of attacks on trucks and cars, despite an impression among truck drivers that such incidents are not uncommon in Aberdeen.
A discussion on Trucknetuk.com has been set up to keep drivers informed about vandalism incidents in the area and offer safety tips for secure parking.