The fire was discovered in a small shed on the site at about 1pm.
Senior Sergeant Dean Harker said two youths were located nearby and have been referred to a youth services agency.
He said the fire started after the youths allegedly dragged some rubbish from outside the shed then set fire to it.
"It was not a large fire and it was able to be put out in a short amount of time," Senior Sergeant Harker said.