EMERGENCY services were called to two cases of suspicious fires in the last week.
A fire destroyed a heritage listed church in Canley Heights on Sunday night.
The roof of the decommissioned church on Canley Vale Road was damaged at 9.30pm.
No one was inside at the time of the incident.
The 4608.5 square metre site was sold in July.
It was DA approved for 24 new town houses and villas with a condition they were to be built around the church.
Police are also investigating a separate incident on Thursday after reports of a blaze in Knight Park in Yennora at 10.45am.
Station officer from Guildford Fire and Rescue Service Darren Gould said at least two plastic bins were set alight which then damaged the roof structure of the shed.
A witness told police three youths aged between 16 to 18 were seen running from the scene.
Any witnesses should contact Cabramatta police on 9725 8999, Fairfield police on 9728 8399.