Firefighters responded to the works yard parking lot off Pipeline Road just after 10:30 p.m. PT. where they found the truck fully engulfed in flames, and two others catching fire.
They quickly extinguished the vehicle fire, but not before it destroyed one truck, significantly damaged two other trucks, and a left a nearby tool shed with minor damage. Police estimated the cost of the property damage to be around $70,000.
The parking lot is adjacent to horse stables used by the Vancouver Police Department's Mounted Unit and the Triple A Horse and Carriage stables.
The stables, horses, and surrounding woods were untouched.
Vancouver police set up roadblocks around the park in an attempt to locate or identify a suspect.
Const. Lindsey Houghton said that investigators determined that the fire was deliberately set.
"Police are working closely with park staff, and officers will be conducting stepped-up patrols in Stanley Park and surrounding areas," he said in a written statement.
This is the second suspected arson in the park's core this week.
On Friday, a fire destroyed the replica station house at the park's miniature train attraction, which is directly across Pipeline Road and next to the site of the old petting zoo.
Vancouver Fire and Rescue Services Captain Gabe Roder had said that investigators determined the train station fire was deliberately set.
Roder also said it was fortunate nearby trees and brush were still damp from recent rain, otherwise the fire could have spread to the surrounding forest.