Whittlesea Crime Investigation Unit detectives are investigating a suspicious grass fire in Epping on Monday 15 January.
Emergency services were called to the fire on Genesis Drive just after 9pm.
Investigators have been told a man was seen walking his dog before walking to the middle of a vacant block and setting the long grass on fire.
He then left the scene on foot, heading south towards Revelation Road.
Investigators have released CCTV of a man they believe can assist with their enquiries.
The man is perceived to be Caucasian, about 180cm tall with a medium build, wearing dark coloured shorts, a black and white t-shirt.
He was walking a small dark-coloured dog with white markings on its chest.
Detectives are also investigating a previous fire at the same location about 7pm on 11 January.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or make a report online at www.crimestoppersvic.com.au.
