Emergency services were called to two separate fires in Hoppers Crossing and Harkness early this morning.
It is understood a garage was set on fire at a home on Woodland Rise in Harkness just before 12.30am.
Police said all occupants of the home were safely evacuated but two cars inside the garage were damaged in the fire.
A short time later, a second garage was set alight on Gracefield Court in Hoppers Crossing, just before 1am.
A vehicle inside the garage was also damaged, police said.
No one was injured in the blaze.
Although the cause of the fires is yet to be determined police believe them to be suspicious.
It is believed the two incidents are linked, police said.
Anyone who may have witnessed either incident or has dashcam/CCTV or information is urged to contact Crime Stoppers on 1800 333 000.