Flames from an open fire spread to a caravan, four lorries and a JCB.
Firefighters were called to Lon Parcwr, Ruthin, after thick black smoke was seen over the business park.
Two fire engines were sent to tackle the burning lorries and the caravan shortly after 2.05pm today, and the fires were out within an hour.
The derelict caravan was destroyed in the blaze and the other vehicles received slight damage.
North Wales Police were also called to the fire in the scrapyard up a trackway.
Nobody was injured in the incident.
It is unknown who the vehicles belonged to.
North Wales Fire and Rescue Service have launched an investigation into the blaze.
A fire service spokeswoman said: “We sent two fire engines to the scene where four light goods vehicles were well alight after we were called at 2.06pm.
“The stop message came at 3.06pm. An investigation found a brazier spread a fire to the caravan which in turn ignited the other vehicles.