A VACANT house was deliberately set alight in Keysborough on Thursday 5 May.
A passer-by noticed a red glow and smelled smoke coming from the Isaac Road home just after 9pm and called triple-zero.
They told police they heard hushed male voices coming from the rear of the premises.
CFA crews attended and extinguished the fire, which caused moderate damage to a north-side room.
Police officers, including the canine unit, also attended and searched the area, but didn’t locate the firebugs.
Greater Dandenong CIU Detective Sergeant Luke Kirton said an arson chemist attended the scene and deemed the cause of the fire suspicious.
He urged anyone with information to call Crime Stoppers on 1800 333 000.
