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.
Cooloongup man accused of historical child sex offences dies just weeks before trial
Boat owners urged to make safety a priority this Easter
Mundijong man accused of attempting to procure children overseas for sexual activity
PM Anthony Albanese to address nation
Mandurah teacher who raped student to remain on bail
Man charged after allegedly exposing himself to girl on Transperth bus in Lakelands
Fire rips through Golden Bay home
Firefighters battle bushfire near Nambeelup
Alcoa Children's Festival cancelled due to severe weather