Three appliances from Baldivis Bushfire Brigade were called to the playground at 2.51am on June 23.
The damage to the 15sq m of playground equipment was initially valued at $20,000, but was later upgraded to $150,000.
Anyone who witnessed anything suspicious in the vicinity of the playground is urged to contact Crime Stoppers on 1800 333 000.
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READ NOWThe vandalism comes less than three months after Waikiki’s Fantasy Park, as well as a Charthouse Primary School cubby house, were set alight about midnight on Tuesday, April 9.