The Arson Squad is investigating after fire damaged heavy machinery at a controversial housing development site in Golden Bay.
Vandals threw a molotov cocktail type device over a fence at around 9:45 last night, causing $400,000 damage to earth moving equipment.
Firefighters contained the blaze within 30 minutes.
Police searched the area however no persons were located.
Demonstrators have been at the site for several days protesting the bulldozing of sand dunes to make way for a housing development.
The Western Australian Planning Commission granted conditional approval for the subdivision of the area, known as 5A, in June this year, with plans for 88 residential lots.
Mandurah detectives are seeking anyone with information about the incident to contact Crime Stoppers on 1800 333 000 or report on line to www.crimestopperswa.com.au

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