A commercial building in Mandurah has gone up in flames overnight.
The fire erupted at the vacant property on Randell Street just before 12.30am on Wednesday.
A smoke alert was issued for nearby residents while firefighters worked to extinguish the blaze.
"The fire caused significant damage to the building which is situated near the corner of Pinjarra Road and Randell Street," a WA Police spokesperson said.
"Due to the size and scale of the fire detectives from the Arson Squad have been deployed to the scene to assist in determining the cause of the fire.
"In the event the fire is confirmed to be subject of criminal activity, rewards of up to $25,000 are available for information that leads to the identification and conviction of an arsonist."
Anyone with information should contact Crime Stoppers on 1800 333 000.
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