The firebug is believed to be responsible at least 25 fires that were deliberately lit in bush and grassland around the Laura Douglas Reserve from December 1 until last week.
Detective Senior Sergeant Michael Gaul said it was fortunate the fires were quickly contained.
“With a strong wind, these fires could pose a major threat to the Dallas residents,” he said.
“We believe the same person or persons are responsible and we are calling on the community to help us catch the arsonist by reporting any suspicious activity to Triple Zero (000) immediately if they see any suspicious behaviour, particularly young males, or anyone on push bikes hanging around that area particularly late at night.
“Even the smallest, seemingly insignificant detail could be vital to solving this case.”
The most recent fires occurred on January 20 with six fires in a 40-minute period between 10pm to 10.40pm in the Dallas area.
A male riding a pushbike was seen in the vicinity of several fires and investigators believe he may be able to assist them with their enquiries.
“Considering the reserve does join a number of residential premises in Dallas, the activity is extremely high risk give the weather conditions we have,” Sergeant Gaul said.
“It wouldn’t take much for the fires to impact the residential premises up there.
“We’re treating it very seriously and the actions of the person are quite dangerous.
“It’s extremely frustrating for those in the fire service as well as for Victoria Police because there’s more of a risk fighting fires at this time of year because of the weather conditions sometimes they create a catastrophic situation.”
He said anyone caught illegally lighting fires could face charges of arson which carries heavy penalties or prison.
Anyone with any information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au
